Last updated: Sunday 30 August 2026 (Europe/London).
Next update: when iD Mobile’s £6 promo ends on 8 September 2026, when spusu’s 20 Special ends on 3 September 2026, when SMARTY, giffgaff or VOXI change the 20GB monthly rate, or when the live SIM hub shows a cheaper same-allowance 12-month total on a retailer page I can open.
By: Switch Editorial Team, Switch Squid Ltd
I am Switch. I compare SIMs for a living, and 20GB SIM only deals UK August 2026 is the search comparison sites keep answering with a filter and a teaser tile that is not on the retailer’s own shop.
uSwitch has no dedicated 20GB URL. You land on the generic SIM hub, tick a data box, and hope the card still means 20GB — and still exists — by the time you check out. This morning’s rewrite is blunt about that: Lebara’s 20GB exclusive and Talkmobile’s 20GB tile are not on lebara.co.uk or talkmobile.co.uk today. I dropped them. Our own SIM only hub is every network and every allowance, ranked by total monthly cost. This page is one tier: 20GB, priced from retailer pages on Sunday 30 August 2026.
The lead is not a comparison exclusive. It is iD Mobile 20GB at £6.00 flat on idmobile.co.uk — 1-month, 12-month and 24-month all at £6 during a new-customer promo running 12 August to 8 September 2026. Twelve months is £72. Average £6.00. That is the year. Not a three-month tease that steps up later.
Ofcom’s Communications Market Report 2026 puts average monthly data per mobile data user at 11.8GB in 2025 (CMR 2026 PDF). So 20GB is the comfortable average-plus bucket, not a heavy-user plan. If last month was 40–90GB, you are shopping the wrong URL — start with 100GB SIM only deals or cheapest unlimited SIM only UK 2026.
I will not invent a 20GB SKU. I will not rank a uSwitch tile that the retailer’s own site does not sell. Every pound in the ranking table below is dated to a retailer page I am standing behind on 30 August 2026.
Filter 20GB on the hub
Open the SIM only hub. Set data around 20GB, pick 30-day or 12-month, sort by total monthly cost. Commission does not move a row. If a 1GB or 5GB card is still sitting on top, you filtered wrong.
Need a new handset instead of airtime? That is a different bill: compare phone deals.
Already sure you want a fat cap or uncapped? The neighbour guides are 100GB SIM only deals UK and cheapest unlimited SIM only UK 2026. This URL stays on 20GB.
What I verified today
Five retailer-verified 20GB (or 20GB-base) plans. Dated Sunday 30 August 2026 unless I say otherwise. Comparison exclusives that are not on the shop today live in the “What I dropped” section, not here.
iD Mobile 20GB, idmobile.co.uk/sim-only-deals, fetched 30 August 2026: £6.00 a month on 1-month, 12-month and 24-month terms during the promo window 12 August–8 September 2026, new customers only. Unlimited UK minutes and texts. No annual price rises. Roam in 50 destinations with a 30GB fair use. Data rollover. Twelve-month total £72.00, average £6.00. This is the lead.
spusu 20 Special, spusu.co.uk/plans (homepage and /plans both match), 30 August 2026: £7.90 a month rolling, special until 03/09/26. Unlimited minutes. EU roam 8GB / 500 minutes. Twelve months at that rate is £94.80 if the price holds after the special ends. Use £7.90, not an older £8.90 figure.
SMARTY 20GB, smarty.co.uk/all-plans, 30 August 2026: £9.00 a month rolling, unlimited UK calls and texts, eSIM, Three network. Twelve-month total £108.00, average £9.00.
giffgaff 20GB Golden Goodybag, giffgaff £10 Golden Goodybag, research-verified 30 August 2026: £10.00 a month rolling. Twelve-month total £120.00, average £10.00. Dated as research-verified if the live fetch is blocked; reopen the URL before you treat the pound as gospel after this morning.
VOXI 20GB base, voxi.co.uk/plans, 30 August 2026: base 20GB at £10 a month; current promo triples data to 60GB until 30 September 2026, then reverts to 20GB; price stays £10. Year £120. Optional fifth row — same cash as giffgaff, more data until the promo ends.
EE note (not in the unlimited-mins ranking table). EE’s 30-Day Saver style 20GB PAYG lands around £9 with auto-renew 10% off a £10 plan on research for ee.co.uk help PAYG plans — but it is 500 minutes, not unlimited, and PAYG often carries a 25Mbps cap. Useful as a big-four alternative in prose. Not the same product as the MVNO rows above, so it stays out of the main table.
What I dropped
Comparison hubs still try to sell these as 20GB. Retailer shops do not. I am naming them so you know I looked.
Lebara 20GB £2.78 then £6.95 on uSwitch — not on lebara.co.uk today. The retailer’s own list is in the 5 / 30 / 50 / 100 / unlimited lane, not a 20GB SKU. Do not rank a comparison exclusive the shop does not sell. Dropped from the table.
Talkmobile 20GB £5.95 on uSwitch — not on talkmobile.co.uk. The shop lists 15GB at £5.95 and 30GB at £6.95 rolling. Nearest Vodafone-host neighbour you can actually buy: Talkmobile 30GB £6.95. That is 30GB. It is not in the 20GB ranking.
uSwitch EE-network “20GB” tile around £6.90 — comparison exclusive / MVNO mix. Prefer the buyable spusu.co.uk Special at £7.90 (to 03/09/26) over a silo pound I cannot match on the retailer’s own checkout this morning.
If a tile is cheaper than iD’s £6 and the retailer’s own site does not print that SKU, the tile is not a deal. It is a trap for people who do not click through.
Ranked by what you actually pay
Four columns. Ongoing rate is what the bill is while the current promo or rolling rate holds. Average is the 12-month total divided by 12. Every row below is retailer-verified on 30 August 2026.
Plan (dated 30 Aug 2026) | Term | Ongoing £ / month | 12-month average |
|---|---|---|---|
iD Mobile 20GB (idmobile.co.uk, promo 12 Aug–8 Sept, new customers) | 1 / 12 / 24-month all £6 in promo | £6.00 flat while promo holds | £6.00 (£72.00 total) |
spusu 20 Special (spusu.co.uk/plans, ends 03/09/26) | Rolling special | £7.90 while special holds | £7.90 (£94.80 if price holds) |
SMARTY 20GB (smarty.co.uk all-plans) | Rolling | £9.00 | £9.00 (£108.00 total) |
giffgaff 20GB Golden Goodybag (giffgaff.com, research-verified 30 Aug) | Monthly rolling | £10.00 | £10.00 (£120.00 total) |
VOXI 20GB base / 60GB promo to 30 Sept (voxi.co.uk/plans) | Rolling | £10.00 (data drops to 20GB after 30 Sept) | £10.00 (£120.00 total) |
£6.00 is the month. £72 is the year. That is the point of this rewrite.
Nano SIM card next to a phone — 20GB SIM only deals ranked by 12-month cash.
iD’s flat £6 undercuts every other retailer-verified 20GB row I can stand behind today. Over twelve months you pay £72. spusu’s Special at £7.90 costs £94.80 if it holds — about £23 more for the EE mast and a hard end date of 3 September 2026. SMARTY at £9 is £108 — £36 more than iD for Three coverage, eSIM and SMARTY’s own checkout. giffgaff and VOXI both land at £120 for the year; VOXI’s temporary 60GB is the reason to pick that row over giffgaff if you are data-hungry until 30 September.
Lebara’s old teaser maths (£2.78 × 3 + £6.95 × 9 = £70.89) would have looked a pound cheaper than iD on a comparison page. It is not on lebara.co.uk this morning. I am not putting a ghost SKU above a live retailer price.
£6 is the year. Promo ends 8 Sept.
If Three coverage works at your postcodes and you pass whatever checkout iD asks for, the cheapest retailer-verified 20GB year I can print today is iD at £6 × 12 = £72. The promo is time-boxed: 12 August to 8 September 2026, new customers. After 8 September, reopen idmobile.co.uk before you treat £6 as live. The card I opened priced 1-month, 12-month and 24-month at the same £6 during the window — so you are not forced into a long lock to bank the rate, but read the checkout term before you assume you can leave on day 31 of a 24-month selection.
If you want EE’s mast and a rolling bill, spusu’s £7.90 Special on spusu.co.uk is the buyable price until 3 September 2026. Do not swap it for a uSwitch EE-silo £6.90 tile unless that pound appears on spusu’s own checkout.
If you want SMARTY’s no-drama Three option — unlimited UK calls and texts, eSIM, cancel anytime — £9 rolling is the direct price. Fair if you want that brand. Not fair if you only looked at a comparison teaser that is not on the retailer.
giffgaff at £10 is the O2-mast rolling Goodybag. VOXI at £10 with 60GB until 30 September is the Vodafone-host cousin with a temporary data bump. Same year cash. Different mast. Different promo clock.
How 20GB actually spends
Ofcom’s 2026 CMR figure is 11.8GB average per mobile data user in 2025. A 20GB SIM is roughly 8GB of headroom above that average — maps, a few HD streams, a week of holiday photos, not a laptop hotspot habit.
Illustrative only, labelled as such: at a rough 3GB per hour for HD streaming, 11.8GB is about four hours of video a month. 20GB is about six to seven hours. Social apps, navigation and app updates eat the rest. If Settings → Mobile Data (iPhone) or the Android data-usage screen showed 18–22GB last month with a week still to go, 20GB is tight. If it showed 8–14GB, you are in the right shop.
Phone data usage at 11.8GB, Ofcom average for a mobile data user.
I am not going to pretend 20GB is “plenty for everyone”. It is plenty for the average-plus user Ofcom is describing. Heavy tetherers belong on the 100GB page.
Rolling vs promo at this tier
At 20GB the retailer-verified set is mostly flat rolling or flat promo — not a three-month teaser that doubles later. iD’s £6 is flat across the terms shown in the promo window. spusu £7.90, SMARTY £9, giffgaff £10 and VOXI £10 are flat monthly rates while those offers hold. Twelve months costs twelve times the monthly. That is why ranking by year cash and ranking by monthly rate land in the same order today.
The clocks still matter. iD’s promo ends 8 September 2026. spusu’s Special ends 3 September 2026. VOXI’s 3× data ends 30 September 2026 (price stays £10; allowance returns to 20GB). Miss the window and reopen the retailer before you screenshot this page into a group chat.
Talkmobile’s nearest verified neighbour — 30GB at £6.95 rolling on talkmobile.co.uk today — is also flat. Ten extra gigabytes for about the same ongoing pound as a mid-table 20GB. If you sit at 22–28GB most months, that 30GB row may beat stretching a 20GB SIM. It still is not a 20GB deal, so it stays out of the ranking table.
You are buying a mast, not a logo
20GB on a dead mast is 0GB. The four UK networks still sit under the MVNO names.
If you want this mast | 20GB plan I named today | Parent | Check before you pay |
|---|---|---|---|
Three | iD Mobile 20GB £6 (lead); SMARTY 20GB £9 | Three | Ofcom checker at home and work. iD promo to 8 Sept, new customers. Rural Three still varies. |
EE | spusu 20 Special £7.90 (to 03/09/26); EE PAYG ~£9 / 500 mins as prose note only | EE | Prefer spusu.co.uk checkout over a uSwitch EE silo tile. EE PAYG is not unlimited mins. |
O2 | giffgaff 20GB Golden Goodybag £10 | O2 | Research-verified 30 Aug on giffgaff’s Goodybag URL. Confirm at checkout. |
Vodafone | VOXI 20GB base £10 (60GB promo to 30 Sept); Talkmobile 30GB £6.95 as neighbour only | Vodafone | Lebara 20GB not on lebara.co.uk today — do not buy the uSwitch ghost. Talkmobile shop is 15/30GB, not 20GB. |
Coverage beats a pound saved. Run the Ofcom checker for the address you sleep at and the address you work at before you celebrate £72.
When to step up to 100GB or unlimited
Stay on 20GB if last month was under about 15GB and you do not hotspot a laptop. Step to 100GB if you regularly clear 20GB, share the phone as a hotspot, or came off a fat phone contract and still watch the allowance. Unlimited is insurance for 80GB+ months, not virtue.
Same morning context, not 20GB rows:
Talkmobile 100GB and other fat-cap maths live on the 100GB guide.
Unlimited ranking: cheapest unlimited SIM only UK 2026 — year averages, not Mozillion 1GB at £2.
I am not going to flatten those into this page’s table. Different search. Different bill.
Roaming at 20GB
UK data does not follow you abroad as the same allowance. Caps I am dating from the retailer-verified cards today:
Plan | Roaming I saw | Data abroad | Dated |
|---|---|---|---|
iD Mobile 20GB | 50 destinations, included | 30GB fair use | idmobile.co.uk, 30 Aug 2026 |
spusu 20 Special | EU roam on the special copy | 8GB / 500 mins | spusu.co.uk/plans, 30 Aug 2026 |
SMARTY 20GB | EU (SMARTY standard terms) | Check SMARTY roam fair use at checkout | smarty.co.uk all-plans, 30 Aug |
giffgaff 20GB Goodybag | giffgaff EU / destinations list | Confirm fair use on the Goodybag page at checkout | research-verified 30 Aug |
VOXI 20GB / 60GB promo | VOXI EU terms | Confirm on voxi.co.uk/plans | voxi.co.uk, 30 Aug |
Talkmobile 30GB neighbour | 47 European destinations | 5GB fair use | talkmobile.co.uk, 30 Aug |
A week in Spain can burn a thin roam cap while 20GB sits unused at home. iD’s 30GB roam fair use across 50 destinations is a real reason to take the £72 year over a cheaper-looking tile with a thinner roam line — after you check the destinations list at checkout.
PAC, eSIM, credit checks
Text PAC to 65075. Free, usually one working day, keeps the number. Give it to the new network at checkout. Do not cancel the old SIM first or the number dies.
Text INFO to 85075 if you are not sure you are out of contract. A cheap 20GB rolling SIM is a bad surprise if you still owe six months on a handset plan.
eSIM: SMARTY’s own plans page today flags eSIM. iD cards often do too — confirm at checkout if you want the SIM this afternoon rather than a 3-in-1 in the post.
Credit checks: SMARTY sells no-credit-check as a feature on its own site. Many short rolling MVNO SIMs are lighter than a 24-month big-four contract, but I am not going to flatten every brand into “never checks”. If a checkout asks for a soft search, read the line before you blame the comparison table. iD’s promo is new customers — expect the checkout to say so.
What I want you to do
Open Compare live SIM only deals on the SIM only hub. Filter around 20GB. If Three coverage works and you can join as a new iD customer before 8 September 2026, iD’s flat £6 (£72 year, idmobile.co.uk, 30 August 2026) is the total to beat. If you want EE and a rolling bill before 3 September, spusu’s Special at £7.90 on spusu.co.uk is the monthly to beat. If you want SMARTY’s own checkout on Three, £9 rolling is the direct price I verified this morning. giffgaff and VOXI both sit at £10 / £120 a year if those masts fit.
Do not buy a Lebara “20GB £2.78” tile from a comparison hub while lebara.co.uk does not list 20GB. Do not buy a Talkmobile “20GB £5.95” card while talkmobile.co.uk sells 15GB at that pound. Do not treat a uSwitch EE-network £6.90 tile as spusu if spusu.co.uk says £7.90.
If the phone has to change, compare phone deals instead. If you need 100GB or unlimited, use those guides. This URL is 20GB, ranked by the year, retailer pages only.
Switch Squid Ltd (company number 13332631) is based in Leamington Spa. We compare. We are not your network. Call 01926 942125 if you want a human to read the table with you.
Frequently asked questions
What is the cheapest 20GB SIM only deal in the UK today?
The cheapest 12-month total I can verify on a retailer page on Sunday 30 August 2026 is iD Mobile’s 20GB at £6.00 a month flat during the 12 August–8 September 2026 new-customer promo on idmobile.co.uk — £72 for the year, average £6.00. Next is spusu’s 20 Special at £7.90 (£94.80 if it holds to a year) on spusu.co.uk until 03/09/26. I am not headlining Lebara or Talkmobile 20GB tiles that those retailers do not sell today.
Why did you drop Lebara and Talkmobile from the ranking?
Because the shops do not sell them. Lebara’s own site lists 5 / 30 / 50 / 100 / unlimited — not 20GB. Talkmobile’s own shop lists 15GB at £5.95 and 30GB at £6.95, not 20GB. A uSwitch exclusive that is not on the retailer is not a SwitchSquid ranking row.
Is iD really £6 on 1-month, 12-month and 24-month?
On the idmobile.co.uk SIM-only deals page fetched 30 August 2026, the 20GB promo priced those terms at £6 during 12 Aug–8 Sept 2026 for new customers. Reopen the page before you assume that still holds after 8 September. Read the term you pick at checkout.
spusu was £6.90 on uSwitch and £7.90 on spusu.co.uk. Which is real?
For this rewrite I am ranking the buyable retailer price: £7.90 Special on spusu.co.uk /plans until 03/09/26 (homepage matches). The uSwitch EE-network tile is treated as a comparison exclusive / mix — dropped from the ranking in favour of the shop.
Does Talkmobile still do 20GB for £5.95?
Not on talkmobile.co.uk this morning. The shop lists 15GB at £5.95 and 30GB at £6.95 rolling. Until the shop and the card agree on a 20GB SKU, I dropped it. The nearest verified neighbour is Talkmobile 30GB at £6.95.
Is 20GB enough if Ofcom says average use is 11.8GB?
For most people, yes — with headroom. Ofcom’s CMR 2026 figure is 11.8GB average per mobile data user in 2025. 20GB is the comfortable average-plus bucket. If you already clear 20GB, move to the 100GB guide. If you blow past 80GB, read cheapest unlimited SIM only UK 2026.
What about EE’s ~£9 20GB PAYG?
Mentioned in prose only. Around £9 with auto-renew 10% off a £10 plan on EE PAYG research, but 500 minutes not unlimited, and a 25Mbps cap is common on that PAYG lane. It is not the same product as the unlimited-mins MVNO rows in the table.
Can I keep my number?
Yes. Text PAC to 65075, pass the code to the new network. Usual transfer is one working day. Do not cancel first.
Should I buy a phone on contract instead?
Only if you need the handset. Airtime at £6–£10 and a flagship at £45–£75 are not the same product. Compare phone deals for the handset total. Come back here for the 20GB SIM.
Sources
iD Mobile, fetched 30 August 2026: SIM only deals — 20GB £6.00 on 1-month / 12-month / 24-month during promo 12 Aug–8 Sept 2026, new customers; unlimited mins/texts; no annual price rises; roam 50 destinations (30GB fair use); data rollover. 12-month total £72 (avg £6).
spusu, fetched 30 August 2026: Plans (homepage and /plans) — 20 Special until 03/09/26; 20GB, unlimited mins, £7.90/mo; EU roam 8GB / 500 mins. 12-month £94.80 if price holds. Use £7.90, not £8.90.
SMARTY, fetched 30 August 2026: All plans — 20GB £9/mo rolling; unlimited UK calls/texts; eSIM; Three network. 12-month £108.
giffgaff, research-verified 30 August 2026: £10 Golden Goodybag — 20GB £10/mo monthly rolling. 12-month £120.
VOXI, fetched 30 August 2026: Plans — 20GB base £10/mo; 3× data promo = 60GB until 30 Sept 2026 then reverts to 20GB; price stays £10. Year £120.
Talkmobile, fetched 30 August 2026: SIM only deals — no 20GB SKU; 15GB £5.95 rolling; 30GB £6.95 rolling; roam 47 European destinations, 5GB fair use. uSwitch Talkmobile “20GB £5.95” treated as stale vs own shop.
Lebara retailer check, 30 August 2026: lebara.co.uk lists 5 / 30 / 50 / 100 / unlimited — no 20GB SKU. uSwitch Lebara 20GB £2.78 then £6.95 exclusive dropped.
EE PAYG research note: ee.co.uk help PAYG plans — ~£9 20GB 30-Day Saver style with auto-renew 10% off £10; 500 mins not unlimited; 25Mbps cap on PAYG. Prose only, not ranked with unlimited-mins MVNOs.
Ofcom Communications Market Report 2026: average monthly data per mobile data user 11.8GB in 2025 — CMR 2026 PDF.
SwitchSquid hubs, linked 30 August 2026: SIM only deals; 100GB SIM only deals UK; cheapest unlimited SIM only UK 2026; phone deals.
Competitor note: uSwitch has no dedicated 20GB URL — 20GB is a filter on the generic SIM hub / network silos only; hub still shows stale Talkmobile/Lebara 20GB tiles that retailer shops do not list today.
