Last updated: Monday 7 September 2026 (Europe/London).
Next update: when Talkmobile changes the 100GB half-price window or the rolling £9.95 card, when iD reprints a labelled 100GB on 12-month or 1-month, when SMARTY’s own 100GB page moves off £12, or when the live SIM hub shows a cheaper retailer-verified 12-month total.
By: Switch Editorial Team, Switch Squid Ltd
I am Switch. I compare SIMs for a living, and 100GB SIM only deals UK September 2026 is the heavy-data rung where comparison hubs still try to sell you a teaser pound that the retailer’s own shop does not print.
We already have an evergreen 100GB SIM only deals UK guide. This URL is the dated September 2026 commercial slug — same allowance, fresh retailer cash, ranked for people searching the month in the query. If you landed here from a September SERP, stay. If you want the evergreen hub, that link is one click away.
Our SIM only hub is every network and every allowance, ranked by total monthly cost. This page stays on 100GB. Neighbour September guides: 50GB, 40GB, 30GB, and cheapest unlimited SIM only UK 2026.
The cheapest retailer-verified labelled-100GB twelve-month cash this morning is Talkmobile’s 12-month 100GB on talkmobile.co.uk/sim-only: £4.98 for the first three months, then £9.95 from 6 December 2026. Twelve months is £104.49 — average £8.71. That is not the rolling price. The rolling twin on the same shop is £9.95 flat — twelve months £119.40.
Ofcom’s Communications Market Report 2026 puts average monthly data per mobile data user at 11.8GB in 2025 (CMR 2026 PDF). So 100GB is roughly eight times the average — hotspot, commute-stream, and “the Airbnb Wi-Fi is a rumour” territory. If Settings showed under 40GB last month, start on 50GB or 40GB instead.
I will not invent a 100GB SKU. I will not rank a uSwitch exclusive the retailer’s own PDP does not sell. Every pound in the ranking table below is dated to a retailer page I opened on Monday 7 September 2026.
Filter 100GB on the hub
Open the SIM only hub. Set data around 100GB, pick 30-day or 12-month, sort by total monthly cost. Commission does not move a row. If a 80GB or 120GB card is sitting on a “100GB” filter, you filtered wrong — or the live feed mixed a neighbour tier.
Need a new handset instead of airtime? That is a different bill: compare phone deals or phone deals hub.
Already sure you want a thinner or fatter cap? Neighbour guides are 50GB SIM only deals UK September 2026, 40GB, 30GB, evergreen 100GB, and cheapest unlimited. This URL stays on the September 100GB cash table.
Switch the SIM, keep the phone — 100GB is about the airtime bill, not a new handset.
What I verified today
Labelled 100GB plans from retailer shops, plus near-tier cards people will confuse with 100GB. Dated Monday 7 September 2026. Near-tier cards (110GB, 120GB) live in the notes, not as fake 100GB rows. Comparison exclusives that are not on the shop today live in “What I dropped”.
Talkmobile 100GB 12 months, talkmobile.co.uk/sim-only, fetched 7 September 2026: first three months £4.98, then £9.95 from 6 December 2026. Unlimited UK minutes and texts. Vodafone network. 5G where available. Roaming in 47 European destinations with a 5GB fair-use line on Talkmobile’s own copy. Twelve-month cash £104.49, average £8.71. Cheapest labelled-100GB year I can print from a retailer shop today. Leave early and you will usually owe the rest of the term — that is the catch on any 12-month SIM.
Talkmobile 100GB 30-day, same shop, fetched 7 September 2026: £9.95 a month rolling. Same unlimited mins/texts and EU roam fair-use line. Twelve-month cash £119.40 if you stay a year. This is the exit-friendly twin of the half-price 12-month card, not a secret cheaper rate.
iD Mobile SIM-Only 100GB 24 Months, idmobile.co.uk/sim-only-deals (JSON-LD Product offers on the page), fetched 7 September 2026: £10.00 a month, 24-month term, labelled 100GB, unlimited minutes and texts, no annual price rises on the deal tags, Three network. Twelve-month cash £120.00 — but you are still locked for months 13–24 at the same rate unless you pay to leave. Same shop also prints 110GB 24 Months at £10.00 (neighbour, more data, same cash) and 120GB 1 Month at £12.00. There is no labelled 100GB on 12-month or 1-month in today’s JSON-LD list.
SMARTY 100GB, smarty.co.uk/plans/100gb-calls-and-data, fetched 7 September 2026: £12.00 a month on SMARTY’s own page. One-month rolling, unlimited calls and texts, 5G/4G, no credit check, no annual price rises, EU roam with a 12GB fair-use line, Three network. Twelve-month cash £144.00. Comparison sites still show £10 in places — I am ranking the own-site pound, not the affiliate tile.
Mozillion 100GB 12-Months, mozillion.com, fetched 7 September 2026: £14.50 a month cash list price. Twelve-month total £174.00. The site also markets “or FREE every month” via app rewards — that is not guaranteed cash, so the ranking uses £14.50. Sibling cards: 24-month £13.95, 1-month £14.95 (£179.40 over twelve months).
spusu 100, spusu.co.uk/plans schema, fetched 7 September 2026: £14.90 a month for 100GB, flexible monthly, EE network, EU roam data allowance printed as 20GB on that tier. Twelve-month cash £178.80 at the headline rate (confirm any first-month credit wording at checkout).
Lebara 100GB 12-Month Plan, lebara.co.uk PDP (model cost + meta), fetched 7 September 2026: £18.00 a month (meta frames it as 10% off the £20 monthly). Twelve-month total £216.00. Vodafone network. Confirm roam and checkout wording — Lebara’s listing SPA is JS-heavy.
Lebara 100GB Monthly Plan, lebara.co.uk PDP, fetched 7 September 2026: £20.00 a month, no-contract style card. Twelve-month total £240.00.
VOXI 100GB, voxi.co.uk/sim-only-plans, fetched 7 September 2026: £20.00 a month rolling, with unlimited social/music/video app buckets on that tier, on the VodafoneThree “Nation’s Network”. Twelve-month cash £240.00. Separate time-limited data boosts on the £10/£15 plans end 30 September 2026 and are not a permanent 100GB SKU.
What I dropped
Comparison hubs and thin “100GB” round-ups still try to sell these as the deal. Retailer shops do not match, or the allowance is not labelled 100GB.
- Lebara 100GB uSwitch exclusive — uSwitch SIM hub (deals last updated 07/09/2026) still prints an Exclusive 100GB tile at £4.78 for three months then £11.95. Lebara’s own PDPs today are £18 / £20. Dropped per retailer-own-site rule.
- SMARTY at £10 on uSwitch / MoneySuperMarket / SimSherpa-style pages — SMARTY’s own 100GB URL prints £12.00 today. Dropped the cheaper comparison pound.
- iD 108GB at £9 — older comparison notes and an on-page “Switch to 108GB” upsell banner. No priced 108GB Product offer in today’s idmobile.co.uk JSON-LD. Dropped until the shop reprints a priced SKU.
- Lycamobile exact 100GB — lycamobile.co.uk JSON-LD offers today jump UK PAYG to 120GB Mega Plus at £10.00. No exact UK 100GB. Neighbour only.
- Talkmobile rolling £8.95 — still appears on stale comparison copy. Talkmobile’s own rolling 100GB this morning is £9.95.
- Mozillion “or FREE” — rewards path, not a guaranteed £0 cash plan for ranking.
If a tile is cheaper than Talkmobile’s shop £104.49 year and the retailer’s own site does not print that exact 100GB 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 becomes after any intro. Average is the 12-month total divided by 12. Every row below is retailer-verified labelled 100GB on 7 September 2026.
| Plan (dated 7 Sep 2026) | Term | Ongoing £ / month | 12-month average |
|---|---|---|---|
| Talkmobile 100GB 12m (talkmobile.co.uk; £4.98×3 then £9.95 from 6 Dec 2026) | 12-month | £9.95 after intro | £8.71 (£104.49 total) |
| Talkmobile 100GB 30-day (talkmobile.co.uk) | 30-day | £9.95 flat | £9.95 (£119.40 total) |
| iD Mobile 100GB 24 Months (idmobile.co.uk; Three; no April rise on tags) | 24-month | £10.00 flat | £10.00 (£120.00 total) |
| SMARTY 100GB (smarty.co.uk own page) | 1-month | £12.00 | £12.00 (£144.00 total) |
| Mozillion 100GB 12-Months (mozillion.com cash list) | 12-month | £14.50 | £14.50 (£174.00 total) |
£104.49 is the Talkmobile 12-month year. £8.71 is that average. £119.40 is Talkmobile rolling for twelve months. £120.00 is iD’s 24-month 100GB year — with a lock that continues past month twelve.
Over twelve months Talkmobile’s half-price 12-month card beats Talkmobile rolling by £14.91, beats iD’s 24-month 100GB by £15.51, and beats SMARTY’s own-site £12 by £39.51. That gap is real cash if you stay. It is not free if you leave in month four.
Neighbours (not exact 100GB rows): iD 110GB 24m @ £10 (same cash as iD 100GB 24m); iD 120GB 1m @ £12 (£144); Lycamobile 120GB Mega Plus @ £10 PAYG (£120) — no exact Lyca 100GB today; Talkmobile 150GB half-price 12-month sits above this band.
12 months is the cheap 100GB. Rolling is the exit
If Vodafone coverage works at your postcodes and you will stay twelve months, the cheapest retailer-verified labelled-100GB year I can print today is Talkmobile’s 12-month plan at £104.49. Unlimited UK minutes and texts. EU roam with that tight 5GB fair-use line — pack a travel eSIM or a day pass if you are abroad for two weeks.
If you want the same mast and allowance without a year lock, take Talkmobile’s £9.95 rolling 100GB — £119.40 if you stay a year. That is the fair exit lead when you are still checking signal at home, or you might buy a handset in three months.
If you need Three coverage, iD’s labelled 100GB 24 Months at £10 is the cheapest exact-100GB Three-mast card I can verify on the shop today — £120 for the year, with a two-year lock. SMARTY’s own-site £12 is the no-credit-check, one-month version of the same parent network. Pay the extra if you want that simplicity in writing on smarty.co.uk. Do not pay it by accident because a comparison card said £10.
100GB is for hotspot and commute streaming — not the Ofcom 11.8GB average.
100GB is not the average. That is the point
Ofcom’s 2026 CMR figure is 11.8GB average per mobile data user in 2025. A 100GB SIM is roughly eight times that average. This URL is for people who hotspot a laptop, stream on the commute, share maps all day on site, or want headroom after a 60–80GB month that kept brushing the ceiling.
Illustrative only, labelled as such: at a rough 3GB per hour for HD streaming, 100GB is about thirty-plus hours of video a month before maps, social apps and updates eat the rest. If Settings → Mobile Data (iPhone) or the Android data-usage screen showed 70–90GB last month with a week still to go, you are in the right shop. If it showed 30–45GB, you are overpaying for headroom — start on the 50GB or 40GB guide instead. If it showed 120GB+ with hotspotting, stop reading capped pages and open unlimited.
I am not going to pretend 100GB is “unlimited in disguise”. Heavy 4K, multi-device hotspotting, or a week abroad under a 5GB roam cap will still bite. That is why the unlimited page exists.
You are buying a mast, not a logo
100GB on a dead mast is 0GB. The four UK networks still sit under the MVNO names.
| If you want this mast | 100GB plan I named today | Parent | Check before you pay |
|---|---|---|---|
| Vodafone | Talkmobile 100GB 12m / rolling; Lebara 100GB; VOXI 100GB | Vodafone (VOXI also on VodafoneThree branding) | Ofcom checker + Talkmobile 5GB roam FUP |
| Three | iD 100GB 24m; SMARTY 100GB £12 own site | Three | Postcode coverage; iD 24-month lock vs SMARTY 1-month |
| EE | spusu 100 @ £14.90; Lyca neighbour 120GB @ £10 | EE | No exact Lyca 100GB today |
| O2 | No labelled 100GB retailer lead verified in this morning’s shop list | O2 | Use the hub filter; do not invent a giffgaff/Tesco 100GB row |
Run your home and commute postcodes on Ofcom’s coverage checker before you fall in love with a logo. National “99%” claims do not fix a basement.
Roaming, eSIM, PAC — the short version
Roaming: Talkmobile’s own copy today includes EU-style roaming in 47 destinations with a 5GB fair-use data line. SMARTY prints a 12GB EU fair-use line on the 100GB plan page. VOXI wants a European Roaming Pass for roam, with app zero-rating behaving differently abroad. Lebara markets EU (and often India) roam on sibling copy — confirm on the 100GB PDP at checkout. If you spend two weeks in Spain every summer, read the fair-use line before the teaser pound.
eSIM: SMARTY, iD, VOXI and several others offer eSIM on modern handsets. Physical multi-size SIMs still arrive in 2–5 days for people who hate QR codes. Either path keeps your number if you bring a PAC.
PAC / keep your number: Text PAC to 65075 from the number you want to keep. You get a code (usually within a minute). Give it to the new network when you activate. Text STAC to 75075 if you are happy to take a new number. Text INFO to 85075 for contract end date and current spend. Switching should complete in one working day once the new network has the code.
Credit checks: Talkmobile’s own FAQ copy says no credit check on its SIM-only deals. SMARTY and Lebara monthly paths are also no-credit-check style. Longer iD / Mozillion contracts may still run checks — read the basket.
FAQ
What is the cheapest 100GB SIM only deal UK in September 2026?
On retailer-own shops this morning, Talkmobile’s 12-month 100GB at £4.98 for three months then £9.95 — twelve-month cash £104.49 (average £8.71). Rolling Talkmobile 100GB is £9.95 (£119.40 / year). iD’s 100GB 24-month is £10 (£120 / year) with a longer lock.
Is SMARTY 100GB £10 or £12?
SMARTY’s own plan page prints £12.00 today. Some comparison sites still show £10. SwitchSquid ranks the own-site pound.
Does Lebara still have a £4.78 100GB exclusive?
uSwitch still shows an Exclusive Lebara 100GB teaser tile. Lebara’s own 100GB PDPs today are £18 (12-month plan) and £20 (monthly). We dropped the exclusive for ranking.
Is there an iD 108GB deal today?
Not as a priced Product offer on idmobile.co.uk’s JSON-LD this morning. The shop does print labelled 100GB 24 Months at £10 and 110GB 24 Months at £10.
How do I keep my number when I switch?
Text PAC to 65075, order the new SIM or eSIM, enter the PAC when you activate. Your old plan cancels when the port completes.
Should I buy 100GB or unlimited?
If you regularly clear 100GB with hotspotting or 4K, open the unlimited guide. If you sit at 60–90GB, 100GB is usually enough headroom without paying unlimited rates.
Where do I compare live cards?
https://www.switchsquid.com/mobile/sim-only-deals/ — filter ~100GB, sort by total monthly cost.
How I will update this page
I re-open Talkmobile, iD, SMARTY, Lebara PDPs, VOXI, Mozillion and spusu when the half-price window moves, when iD reprints a shorter-term 100GB, or when SMARTY’s own page leaves £12. I will not “refresh” this URL with a comparison exclusive that fails the retailer shop test. The evergreen 100GB guide stays for undated search; this September slug stays for dated cash.
Go compare 100GB for real
Open the hub, filter around 100GB, and sort by what you actually pay over twelve months — not the teaser month, not the commission weight.
Compare live SIM only deals on SwitchSquid →
If the handset is the point, start on phone deals instead. If 100GB is more than you use, drop to 50GB or 40GB. If 100GB is not enough, go unlimited.
