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Updated: 5 November 2026
Prices checked 5 Nov 2026. SIM-only deals move quickly, so confirm the live price and terms on the network’s own site before you switch.
If your phone’s paid off, a SIM-only deal is usually the cheapest way to stay connected. Below are current UK plans we could verify today across Vodafone, EE, O2, Smarty and giffgaff — data, monthly price, contract length and what happens to the price later. We haven’t signed up to these ourselves; every figure comes from the network’s public pages on 5 Nov 2026.
Three, Voxi and iD Mobile are left out of this draft because their sites blocked or failed our checks today. We’d rather leave a gap than guess.
Best SIM-only deals UK compared (checked 5 Nov 2026)
| Product | Key spec | UK price at time of writing | Best for | Link |
|---|---|---|---|---|
| O2 Unlimited Plus (24-month) | Unlimited data; rises Apr 2027/2028 | £19.99/mo (checked 5 Nov 2026) | Heavy data on O2 | O2 SIM deals |
| O2 Classic 75GB (24-month) | 75GB; Black Friday listing; rises Apr 2027/2028 | £18/mo (checked 5 Nov 2026) | Mid-pack data on O2 | O2 SIM deals |
| Vodafone Unlimited Plus (24-month) | Unlimited; EU roam 52 destinations (25GB); rises Apr 2027/2028 | £26/mo (checked 5 Nov 2026) | Unlimited with EU roaming | Vodafone SIM-only deals |
| Vodafone 120GB | 120GB; unlimited mins & texts; rises Apr 2027/2028; confirm term at checkout | £21/mo was £26 (checked 5 Nov 2026) | High data without unlimited | Vodafone SIM-only deals |
| Smarty 100GB (rolling) | 100GB; 1-month rolling; no annual price rises (Smarty) | £12/mo (checked 5 Nov 2026) | Flexible, fixed monthly price | Smarty plans |
| Smarty Unlimited (rolling) | Unlimited data; unlimited UK & EU calls/texts; no annual rises | £20/mo (checked 5 Nov 2026) | Unlimited without a long contract | Smarty plans |
| giffgaff 25GB (18-month) | 25GB; 18-month; check minutes and texts on the plan page | £10/mo (checked 5 Nov 2026) | Low monthly cost, lighter data | giffgaff SIM-only |
The deals worth a look
1. O2 Unlimited Plus — £19.99/month (24 months)
Data: Unlimited. Price: £19.99 a month on a 24-month plan, rising to £22.49 in April 2027 and £24.99 in April 2028 (O2’s listing). Best for: heavy users who want O2 coverage without a handset deal. Why it’s worth a look: unlimited data under £20 at the start of the term is strong, but budget for the April rises. See O2 SIM deals
2. O2 Classic 75GB — £18/month (24 months)
Data: 75GB. Price: £18 a month on a 24-month Classic Plan, rising to £20.50 in April 2027 and £23 in April 2028. Best for: most people who stream a fair bit but don’t need unlimited. Why it’s worth a look: a clear mid-pack price if 75GB is enough. See O2 SIM deals
3. Vodafone Unlimited Plus — £26/month (24 months)
Data: Unlimited (plan text also notes a maximum download of 100 Mbps on this tier). Price: £26 a month on a 24-month plan (Vodafone quotes a £312 saving), rising to £28.50 on 1 April 2027 and £31 on 1 April 2028. Inclusive roaming in 52 European destinations (25GB). Best for: unlimited data with EU roaming baked in. Why it’s worth a look: clearer roaming than many rivals, if you’re happy paying more than O2’s unlimited promo. See Vodafone SIM-only deals
4. Vodafone 120GB — £21/month
Data: 120GB; unlimited minutes and texts. Price: £21 a month (shown as was £26), then £23.50 on 1 April 2027 and £26 on 1 April 2028. Contract: Vodafone’s SIM-only page lets you filter 24 months or 30 days — confirm which you’re buying at checkout. Best for: high data without jumping to unlimited. Why it’s worth a look: a solid mid-high allowance if the £21 headline still shows. See Vodafone SIM-only deals
5. Smarty 100GB — £12/month (rolling)
Data: 100GB on a rolling monthly plan. Price: £12 a month. Smarty states it doesn’t do annual price rises on rolling one-month plans. Best for: people who want to keep control and avoid April bumps. Why it’s worth a look: simple pricing and an easy exit. See Smarty plans
6. Smarty Unlimited — £20/month (rolling)
Data: Unlimited. Smarty also states unlimited UK and EU calls and texts, with up to 12GB of your allowance for EU roaming. Price: £20 a month, rolling, with no annual price rises on that rolling plan (Smarty’s wording). Best for: unlimited data without a long contract. Why it’s worth a look: predictable bill and no 24-month lock-in. See Smarty plans
7. giffgaff 25GB — £10/month (18 months)
Data: 25GB. Price: £10 a month on an 18-month contract (listed under “Our favourites”). Minutes/texts: check the plan page before you buy. giffgaff also listed a 20GB plan at £10 a month with no contract. Best for: lighter data use at a low monthly price. Why it’s worth a look: cheap entry if 25GB is enough and you’re fine on giffgaff/O2 coverage. See giffgaff SIM-only
How to choose a SIM-only deal
- Coverage first. The cheapest plan is useless if it drops calls on your commute. Check the network’s coverage map for your postcode (and the parent network for MVNOs (giffgaff states it is powered by O2; confirm Smarty’s host network on its coverage pages)).
- Data you’ll actually use. 20–40GB covers a lot of people; unlimited only pays if you hotspot or stream heavily.
- Contract vs rolling. 18–24 month deals are usually cheaper up front but raise in April (or March on EE). Rolling plans (Smarty, some giffgaff) cost a bit more per gig but skip the annual bump and are easier to leave.
- Read the price-rise line. If a page shows £X now, £Y next April and £Z the April after, budget for Y and Z — not just X.
- Porting. You can usually keep your number. Ask your current network for a PAC before you order.
FAQ
What is a SIM-only deal?
A mobile plan that gives you data, minutes and texts without bundling a new phone. You use a handset you already own (or buy SIM-free).
Are SIM-only deals cheaper than phone contracts?
Usually, once your phone is paid off. You’re not funding a handset in the monthly bill.
Do SIM-only prices go up every year?
Many 12–24 month plans from the big networks rise in March or April by amounts shown on the deal page. Some rolling MVNO plans, such as Smarty’s, say they do not do annual rises.
Can I keep my number when I switch?
Yes. Request a PAC from your current network and give it to the new one when you activate.
Which UK networks did you check?
Vodafone, EE, O2, Smarty and giffgaff on 5 Nov 2026. Three, Voxi and iD Mobile could not be verified from their sites that day.
Verdict
For raw unlimited value on a big network today, O2’s £19.99 Unlimited Plus stands out — with eyes open to the April rises. If you want to avoid those rises, Smarty’s rolling plans are the cleaner story. EE’s flash sale has ended, so check the current EE SIM-only plans before you decide. We’d rather skip Three, Voxi and iD than invent figures. Read how we test and choose products for how we approach buying guides; this one is researched from public network pages, not a hands-on trial of every SIM.