Last updated: 5 November 2026.
Next update: when Smarty’s public Unlimited price moves, or when giffgaff’s 40GB £8 plan changes price.
By: Switch Editorial Team, Switch Squid Ltd
Prices: on 1 November 2026, giffgaff 40GB was £8 a month on an 18-month plan, and its 25GB plan was £10 a month on the same term. giffgaff says the 40GB for £8 plan is for sign-ups before 4 December 2026. On 9 October 2026, Smarty Unlimited was £20 a month and O2 Classic Unlimited £23 a month. Here’s how giffgaff and Smarty compare.
As of 9 October 2026, Smarty is the cheaper route to true Unlimited at £20 a month on a 30-day rolling plan (Three), while giffgaff’s best data value is 40GB for £8 a month on an 18-month plan (O2), with 25GB for £10 a month on the same term, as listed on 1 November 2026. On SMARTY’s site on 1 November 2026, its smaller plans were £8 for 32GB and £6 for 5GB, also 30-day rolling. If you want Unlimited on O2, O2 Classic Unlimited was £23 a month for 24 months, a limited-time price O2 listed on 1 November 2026. Related: SIM-only deals. There’s no single winner: coverage, contract length and how much data you really use decide it.
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giffgaff 40GB — £8/mo · 18-month plan
- 40GB of 5G data, unlimited UK calls & texts, £8 a month as listed on giffgaff.com on 4 November 2026, for sign-ups before 4 December 2026
- 18-month plan on O2’s network (giffgaff)
- giffgaff says the 40GB for £8 plan is for sign-ups before 4 December 2026. Confirm the £8 price and plan terms on giffgaff.com before you pay
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 price table is irrelevant. If O2 is patchy where you live, any giffgaff plan 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 really need Unlimited. If you’d rather avoid a long contract, compare Smarty Unlimited at £20 with Smarty’s £8 plan, which was listed with 32GB on 1 November 2026. If you’re happy to commit, weigh giffgaff 40GB at £8 for 18 months against O2 Classic Unlimited at £23 for 24 months (a limited-time price O2 listed on 1 November 2026).
Price table (prices as listed on 9 October 2026)
Plan | Data | £/month | Term | Network | EU roaming note | Status / catch |
|---|---|---|---|---|---|---|
Smarty Unlimited | Unlimited | £20 | 30-day rolling | Three (Smarty) | Up to 12GB EU on Smarty’s plan pages | No long contract |
O2 Classic Unlimited | Unlimited | £23 | 24 months | O2 | Confirm on o2.co.uk | Limited-time price listed on 1 November 2026; rises £2.50 each April |
Smarty 32GB | 32GB | £8 | 30-day rolling | Three (Smarty) | Confirm in the basket | No 18-month lock; 32GB listed on 1 November 2026 |
Smarty 5GB | 5GB | £6 | 30-day rolling | Three (Smarty) | Confirm in the basket | Best when Wi-Fi covers your evenings |
giffgaff 40GB (18-month) | 40GB | £8 | 18 months | O2 (giffgaff) | Confirm on giffgaff.com | Sign up before 4 December 2026 |
Smarty Unlimited — £17/mo · 1-month rolling
- Unlimited data with unlimited UK calls & texts on Three’s network, as listed on Smarty’s site on 4 November 2026
- £17 a month when you open Smarty from this page (£20 on Smarty’s own site), and you can leave any month
- Main limitation: 12GB EU roaming fair use. Check Three’s coverage at your postcode and confirm £17 on Smarty’s page before you pay
Unlimited plans still carry fair-use terms on the retailer pages, so read them before you treat a phone as a home broadband replacement.
Who should pick Smarty Unlimited
Pick Smarty Unlimited when Three covers you well and you don’t want any data cap. On 1 November 2026 it was £17 a month with the Smarty Unlimited deal button on this page, or £20 on Smarty’s own site.
Pick Smarty 32GB at £8, as listed on 1 November 2026, when Three covers you and 32GB is honestly enough. Over a year that is about £96 if the price holds. Pick Smarty 5GB at £6 if evenings are Wi-Fi-heavy and you only need a commute cushion.
Smarty’s plans are all 30-day rolling and paid in advance, which suits renters, new graduates and people mid-move. It’s still worth checking your plan every few months in case a cheaper one suits your usage better.
Who should pick O2 Classic Unlimited
Pick O2 Classic Unlimited at £23 a month for 24 months when O2 coverage is solid where you live and work and you want Unlimited on O2’s own network. O2 listed this as a limited-time price on 1 November 2026, so check O2’s page for the price on the day you order. It rises £2.50 each April.
Roaming, 5G, eSIM and fair use
Roaming is where shoppers get surprised. For giffgaff’s 40GB £8 plan, confirm the current EU roaming allowance on giffgaff.com before you treat it as a travel plan. Smarty’s plan pages advertise up to 12GB of EU roaming from your monthly allowance on many plans; check the exact terms on the page you open.
5G depends on the network and your handset. eSIM availability differs by device and retailer, so check during the order. Fair-use terms on Unlimited plans exist for a reason: tethering a whole household all month can break a retailer’s policy. Read the plan page rather than relying on the headline.
Contract vs rolling — exit maths
Rolling plans let you leave at a month’s notice; contracts lock you in but often cost less a month. Compare the monthly price, the term and any April price rises in the basket on the day you buy, rather than the headline alone.
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 24 months.
When giffgaff 40GB at £8 is the smarter “Unlimited” refusal
If you do not need Unlimited at all, giffgaff’s 40GB plan at £8 a month (18 months, O2 network) costs far less than either Unlimited plan, and giffgaff says the 40GB for £8 plan is for sign-ups before 4 December 2026. If you need more than 40GB, our giffgaff alternatives guide compares bigger plans. It is an 18-month commitment, so check O2 coverage first. If you would rather pay £6 with no long contract, Smarty 18GB at £6 a month with our deal button on a 1-month rolling plan is the pick in our £6 SIM guide; this page stays focused on the Unlimited decision.
Final pick card
Choose Smarty Unlimited when you need Unlimited on Three: £17 a month with the deal button on this page, as listed on Smarty’s site on 4 November 2026, or £20 on smarty.co.uk.
Choose O2 Classic Unlimited on a 24-month plan when you want Unlimited on O2, and check O2’s page for the price on the day you order (O2 listed £23 as a limited-time price on 1 November 2026).
Choose Smarty 32GB £8 if Three is strong and 32GB is enough (listed on 1 November 2026).
Choose Smarty 5GB £6 if you mostly use Wi-Fi.
Choose giffgaff 40GB £8 / 18 months if O2 is strong and 40GB covers you (deal button near the top).
Want lots of data without a long contract?
Smarty 100GB — £10/mo · 1-month rolling
- 100GB of 5G and 4G data with unlimited UK calls & texts on Three’s network, as listed on Smarty’s site on 4 November 2026
- £10 a month when you open Smarty from this page (£12 at Smarty’s standard price), no credit check and no annual price rises
- Main limitation: Three’s network, not O2. Check coverage at your postcode first, then confirm £10 on Smarty’s page
FAQ
Is giffgaff or Smarty better for unlimited data in 2026?
Neither is better for everyone. Smarty wins on Three if Unlimited at £20 or 32GB at £8 (listed on 1 November 2026) suits you. giffgaff 40GB at £8 (18 months) is the cheaper choice on O2 if 40GB is enough, and O2 Classic Unlimited on a 24-month plan is the O2 Unlimited option (O2 listed it at £23 as a limited-time price on 1 November 2026). Check coverage first, then contract length, then data.
What data plans does giffgaff sell?
On 1 November 2026, giffgaff 40GB was £8 a month on an 18-month plan, and its 25GB plan was £10 a month on the same term. giffgaff says the 40GB for £8 plan is for sign-ups before 4 December 2026. It also sells rolling monthly plans. Confirm on giffgaff.com before you pay.
Where can I buy Smarty Unlimited?
You can buy it on smarty.co.uk or with the Smarty Unlimited deal button on this page. On 4 November 2026 it was £17 a month on a 1-month rolling plan with the button, as listed on Smarty’s site, or £20 on Smarty’s own site. It runs on Three’s network, so check coverage at your postcode first.
How much EU roaming do I get?
For giffgaff’s 40GB £8 plan, check the roaming allowance on giffgaff.com. Smarty’s plan pages often cite up to 12GB of EU roaming on many plans. Always read the terms in the basket before you travel.
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 or O2 Classic Unlimited if O2 works indoors where you live, or another network that does.
What is the cheapest SIM for light users?
On 28 October 2026, Smarty 18GB was £6 a month with our deal button on a 1-month rolling plan, the pick in our £6 SIM guide. iD Mobile 15GB was also £6 a month on a 1-month plan on iD Mobile’s own site. Confirm the price in the retailer’s basket before you pay.
Affiliate disclosure: SwitchSquid may earn a commission when you buy through the deal buttons on this page.
