Last updated: Saturday 26 September 2026 (Europe/London).
Next update: after giffgaff’s Unlimited join window closes on 2 October 2026, or when Smarty’s public Unlimited price moves.
By: Switch Editorial Team, Switch Squid Ltd
As of 26 September 2026, if you are comparing giffgaff vs Smarty for unlimited (or near-unlimited) SIM-only use in the UK, the honest split is this: giffgaff’s Unlimited 18-month plan is listed at £14/month if you join by 2 October 2026 (then reverts toward the higher standard price after the benefit period), giffgaff’s Unlimited monthly rolling plan is listed at £20/month for 12 months of discount, and Smarty’s live affiliate paths we can send you to today are 40GB for £7 and 18GB for £6 on one-month rolling Three coverage — Smarty’s public Unlimited at £20 has no affiliate money button in this guide. Related: SIM-only deals. There is no single “best overall” winner — coverage, contract appetite and real data use decide it.
We may earn a commission if you buy through our links.
Check giffgaff Unlimited £14 (18-month) →
Check Smarty 40GB £7 rolling →
Quick decision frame
Start with the radio, not the marketing. giffgaff rides O2. Smarty rides Three. If your home, commute and parents’ house sit on weak Three cells, Smarty’s cash table is irrelevant. If O2 is patchy where you live, giffgaff’s £14 Unlimited will still frustrate you. Run Ofcom’s mobile coverage checker for the postcodes that matter before you fall in love with a monthly fee.
Then decide whether you will sign 18 months. That single yes/no separates giffgaff’s cheapest Unlimited from every rolling alternative. If you refuse contracts, compare giffgaff’s £20 Unlimited rolling against Smarty’s public Unlimited £20 and against Smarty’s capped 40GB £7 — not against an imaginary “best network” trophy.
Cash table (checked 26 September 2026)
| Plan | Data | £/month | Term | Network | EU roaming note | Join / catch |
|---|---|---|---|---|---|---|
| giffgaff Unlimited contract | Unlimited UK data* | £14 | 18 months | O2 (giffgaff) | Up to 5GB EU per plan footnotes | Join by 2 October 2026; discount locked for benefit period |
| giffgaff Unlimited rolling | Unlimited UK data* | £20 | Monthly rolling (12 months discount) | O2 (giffgaff) | Up to 5GB EU | Join by 2 Oct 2026 for the promo window |
| Smarty 40GB (affiliate path) | 40GB | £7 | 1 month rolling | Three (Smarty) | Confirm on basket; Smarty public pages often cite up to 12GB EU on many plans | No 18-month lock; re-check voucher landing |
| Smarty 18GB (affiliate path) | 18GB | £6 | 1 month rolling | Three (Smarty) | Confirm on basket | Best when Wi-Fi carries evenings |
| Smarty Unlimited (public shop) | Unlimited | £20 | 1 month rolling | Three (Smarty) | Up to 12GB EU on public plan pages | Educational only here — no affiliate money button in this guide |
| giffgaff 25GB £6 exclusive (soft alt) | 25GB | £6 | Monthly rolling | O2 (giffgaff) | 2GB EU roaming (not 5GB) | Window through 8 October 2026 09:00 UK — only if 25GB is enough |
*Unlimited plans still carry fair-use footnotes on the retailer pages — read them before you treat a handset as a home broadband replacement.
Check giffgaff Unlimited £20 rolling →
Check Smarty 18GB £6 rolling →
Who should pick giffgaff Unlimited
Pick the £14 18-month Unlimited plan when O2 coverage is solid, you will stay put for 18 months, and you truly burn past 40–100GB most months (hotspot weeks, short-form video commute, tablet tethering). The cash gap versus Smarty 40GB at £7 is large on paper — £14 vs £7 — but Unlimited removes the data anxiety that makes some people over-buy mid-tier caps every month.
Pick the £20 rolling Unlimited when you want the same O2 radio without an 18-month signature. Like-for-like against Smarty’s public Unlimited £20, the monthly fee is similar; the differentiators become coverage, EU roaming footnotes (giffgaff’s Unlimited pages cite up to 5GB EU; Smarty’s public Unlimited often cites up to 12GB) and whether you prefer giffgaff’s community support model or Smarty’s app-led dashboard.
Do not pick giffgaff Unlimited “because Unlimited sounds premium” if your last three bills show under 20GB. You are paying for a ceiling you do not touch.
Who should pick Smarty instead
Pick Smarty 40GB at £7 when Three covers you and 40GB is honestly enough. Over a year that is about £84 if the list holds — far below £14×12 or £20×12 Unlimited maths. Pick Smarty 18GB at £6 if evenings are Wi-Fi-heavy and you only need a commute cushion. Use Smarty’s public Unlimited £20 page only when you already trust Three, refuse any data cap, and accept that this guide will not put an affiliate Get deal button on that SKU today.
Smarty’s whole product shape is one-month rolling and pay-in-advance. That helps renters, new graduates and people mid-move. It also means you must calendar a monthly re-check so a voucher expiry does not quietly worsen your cash path.
Roaming, 5G, eSIM and fair use
Roaming is where shoppers get surprised. giffgaff’s Unlimited plan pages (26 Sep 2026) describe EU roaming up to 5GB with out-of-bundle rates after that. The separate 25GB £6 affiliate exclusive is stricter: 2GB EU roaming, not 5GB — disclose that before you buy it as a “travel plan”. Smarty’s public plan pages commonly advertise up to 12GB EU roaming from the monthly allowance on many SIMs — confirm the exact footnote on the landing you open.
5G follows the host network and your handset. eSIM availability differs by device and retailer journey — check the order flow. Fair-use language on Unlimited plans exists for a reason: continuous tethering for a whole household can trip retailer policies. Read the plan page; do not invent “no limits ever” claims from a headline.
Contract vs rolling — exit maths
An 18-month giffgaff Unlimited at £14 saves cash only if you stay. Leaving early can trigger remaining charges — treat the contract length as a real liability, not a footnote. Rolling plans (giffgaff £20 Unlimited, all Smarty rows here) let you leave after a billing cycle, which is worth money if you might move abroad, change jobs, or twin a work handset later.
Illustrative Year-1 airtime only (no handset debt, assuming promo prices hold as marketed): giffgaff £14×12 = £168; giffgaff £20×12 = £240; Smarty 40GB £7×12 = £84; Smarty 18GB £6×12 = £72; Smarty Unlimited £20×12 = £240. Re-check the live basket on purchase day — affiliate voucher landings can drift.
Soft alternative — giffgaff 25GB £6 (2GB EU; window to 8 Oct) →
Switching with a PAC or STAC
Text PAC to 65075 to keep your number, or STAC to 75075 if you are leaving without it. Order the new SIM, activate it, then complete the port. Keep the old SIM until banking OTPs survive the cutover. Ports usually complete by the next working day or a chosen date once submitted — follow the retailer’s own steps.
Coverage homework before you click
Check Ofcom’s coverage map for home, work and the relative you visit monthly. Ask friends on O2 and Three in the same postcodes what indoor signal feels like — outdoor 5G icons lie. If you travel by train through known dead zones, test a day with a friend’s SIM in dual-SIM mode before you commit 18 months.
When the 25GB £6 exclusive is the smarter “Unlimited” refusal
If you do not need Unlimited at all, giffgaff’s affiliate exclusive 25GB for £6 monthly rolling (window through 8 October 2026 09:00 UK) can beat both Unlimited stories on cash — with the hard catch of 2GB EU roaming. It is not a travel SIM. It is a UK-data bargain for Wi-Fi-heavy users who still want O2. see also our dedicated 25GB guide if that is your shape; this page stays focused on the Unlimited decision.
Final pick card
Choose giffgaff £14 Unlimited if O2 is strong and you will stay 18 months for true uncapped UK data.
Choose giffgaff £20 Unlimited rolling if you want O2 Unlimited without the contract.
Choose Smarty 40GB £7 if Three is strong and 40GB is enough.
Choose Smarty 18GB £6 if you live on Wi-Fi.
You can also check Smarty Unlimited £20 on smarty.co.uk only when you need Three Unlimited and accept no affiliate button here.
Consider 25GB £6 only if 25GB + 2GB EU fits — and the window is still open.
Get giffgaff Unlimited £14 (join by 2 Oct) →
FAQ
Is giffgaff or Smarty better for unlimited data in 2026?
Neither is universally better. giffgaff wins on O2 Unlimited cash if you will sign 18 months at £14 (join by 2 October 2026). Smarty wins on Three if 40GB at £7 is enough, or if you want rolling flexibility. Coverage first, then term, then data.
What is the giffgaff Unlimited join deadline?
giffgaff’s help and plan pages state you can get the discounted Unlimited offers until 11.59pm on 2 October 2026. After that, Unlimited returns toward standard prices. Confirm on the retailer plan page before you pay.
Does Smarty have an unlimited affiliate deal on SwitchSquid today?
Not in this guide. We link Smarty’s 40GB £7 and 18GB £6 affiliate paths. Public Unlimited at £20 on smarty.co.uk is educational context only here.
How much EU roaming do I get?
giffgaff Unlimited pages cite up to 5GB EU. The separate 25GB £6 exclusive cites 2GB EU — not 5GB. Smarty public pages often cite up to 12GB EU on many plans. Always re-read the basket footnotes.
Can I keep my number?
Yes. Text PAC to 65075, then complete the new network’s port steps after activation.
Should I take Unlimited if I use about 25GB?
Usually no. Price a 25–40GB rolling plan first. Unlimited is for people who repeatedly hit caps or hotspot heavily.
What if Three coverage is weak at home?
Skip Smarty for that address. Compare giffgaff (O2) or another host network that actually works indoors.
Is the 25GB £6 deal still on?
As of 26 September 2026 the affiliate exclusive window runs to 8 October 2026 09:00 UK. Re-check the offer page; after expiry, do not treat this CTA as current.
Check giffgaff Unlimited £20 rolling →
Affiliate disclosure: SwitchSquid may earn a commission when you use our tracked links. Informational hub links never replace the Get deal buttons. Always confirm plan name, data, term and fee on the retailer basket before you pay.
