Last updated: 27 October 2026
By: Switch Editorial Team, Switch Squid Ltd
When we checked on 27 October 2026, iD Mobile 25GB was £6 a month through our link on a 30-day rolling plan, which is £72 over 12 months if the price stays the same. On iD’s own site the same day, its 12-month 25GB plan was £7 a month, which is £84 over 12 months (£7 × 12), and Smarty’s own 20GB plan was £9 a month, £108 over a year.
We may earn a commission if you buy through the deal buttons on this page. It does not change the price you pay.
iD Mobile 25GB SIM — £6 a month through our link, 30-day rolling
- 25GB of data with unlimited UK minutes and texts, when we checked on 27 October 2026
- £0 to pay upfront, then £6 a month — £72 over 12 months if the price stays the same, and you can leave any month
- iD runs on Three’s network, so check coverage at your postcode first. Confirm 25GB and £6 in the iD basket before you pay
12-month cost compared
Plan (when we checked on 27 October 2026) | Term | Monthly price | 12-month cost |
|---|---|---|---|
iD Mobile 25GB, through our link | 30-day rolling | £6 | £72 |
Smarty 18GB, through our link | 1-month rolling | £6 | £72 |
iD Mobile 15GB on iD’s own site | 1-month rolling | £6 | £72 |
iD Mobile 25GB on iD’s own site | 1-month rolling or 12 months | £7 | £84 |
Mozillion 30GB | 1-month rolling | £7.90 | £94.80 |
Smarty 20GB on Smarty’s own site | 1-month rolling | £9 | £108 |
Lyca Mobile 30GB | 30 days | £5 for the first 30 days, then £10 | £115 (£5 + 11 × £10) |
Lebara 30GB | 30 days | £10 | £120 |
Every 12-month cost assumes the monthly price stays the same. Lyca and Lebara charge every 30 days, so their figures cover 12 periods of 30 days. Figures marked “through our link” are only available through the deal buttons on this page.
Why a 12-month contract does not pay at this size
iD’s own site listed 25GB at £7 a month on its 12-month plan and at £7 on its 1-month plan, when we checked on 27 October 2026. The contract adds a 12-month commitment without lowering the price, and the 30-day rolling plan through our link is £1 a month cheaper. On iD’s own site, the cheapest 12-month plan was 12GB for £6.
Smarty 40GB SIM — £7 a month through our link, 1-month rolling
- 40GB with unlimited UK calls and texts on Three’s network, when we checked on 27 October 2026
- £7 a month with nothing to pay upfront — £84 over 12 months if the price stays the same
- Twice the data of a 20GB plan for £1 a month more. Confirm 40GB and £7 on Smarty’s page before you pay
Is 20GB enough?
Ofcom’s 2026 report puts typical UK mobile use at around 12GB a month, so 20GB to 25GB leaves room for maps, social media and some video. If you hotspot a laptop or stream a lot on mobile data, look at 40GB instead.
eSIM or physical SIM?
iD Mobile and Smarty both offer eSIM on compatible phones, which can be active within minutes. A physical SIM usually arrives in two to three working days. Check your phone is unlocked before you order either.
Price rises
iD Mobile and Smarty both say their SIM plans have no annual price rises. Rolling plans can still change price with notice, but you can leave when they do. On a fixed contract, read the contract summary for any rise shown in pounds and pence.
How to buy
Check coverage on Three’s network for iD and Smarty.
Confirm the data and price in the basket before you pay.
Text PAC to 65075 to keep your number.
Our SIM only deals page compares more sizes and networks.
Smarty 18GB SIM — £6 a month through our link, 1-month rolling
- 18GB with unlimited UK calls and texts on Three’s network, when we checked on 27 October 2026
- £6 a month with nothing to pay upfront — £72 over 12 months if the price stays the same
- Just under 20GB for £6 a month, with no contract. Confirm 18GB and £6 on Smarty’s page before you pay
FAQ
What is the cheapest 20GB SIM only deal in the UK?
When we checked on 27 October 2026, iD Mobile 25GB was £6 a month through our link on a 30-day rolling plan, £72 over 12 months. Smarty 18GB was also £6 a month through our link.
How much is iD Mobile’s 12-month 25GB plan?
iD’s own site listed it at £7 a month when we checked on 27 October 2026, which is £84 over 12 months (£7 × 12).
Does Smarty 20GB have a contract?
No. Smarty plans are 1-month rolling. When we checked on 27 October 2026, Smarty’s own site listed 20GB at £9 a month.
Should I take a 12-month SIM or a rolling plan?
At this size, rolling usually costs the same or less. iD’s own site listed 25GB at £7 on both its 1-month and 12-month plans when we checked on 27 October 2026.
Which network do iD Mobile and Smarty use?
Both run on Three’s network. Check coverage at your home and work postcodes first.
Can I keep my number?
Yes. Text PAC to 65075 and give the code to your new network.
