June 2026
If you already own your phone — or you have just bought a refurbished one — a SIM only deal is almost always cheaper than a contract that bundles a handset. You are not paying off a phone you do not need, and you are free to switch whenever a better deal appears.
The UK SIM only market is competitive. Networks are fighting hard for customers and prices have fallen significantly over the past two years.
Data allowance — the average UK smartphone user uses around 6GB per month. If you are on Wi-Fi at home and at work, a 20–30GB plan is plenty. If you stream heavily on the go, go unlimited.
Contract length — 30-day rolling plans cost slightly more per month but let you leave at any time. 12-month plans offer better value but lock you in.
Network coverage — EE has the widest 4G coverage in the UK. Three has the most aggressive unlimited data pricing. O2 and Vodafone sit in the middle on both.
Roaming — if you travel regularly, check what is included. Some SIM only plans include European roaming, others charge extra.
### Honest Mobile
Honest Mobile runs on Three's network, offers genuinely unlimited data plans, and plants trees with every subscription. Their pricing is competitive and their 30-day rolling contracts mean no long-term commitment.
Best for: Eco-conscious users who want unlimited data and flexibility.
### Smarty
Smarty runs on Three's network and is consistently one of the cheapest SIM only options in the UK. Their unique selling point is that unused data is credited back to your account each month. No contracts, just 30-day rolling plans.
Best for: Budget-conscious users who want maximum flexibility and fair pricing.
### 1pMobile
1pMobile operates on EE's network — the UK's best coverage — at significantly lower prices than EE itself. You pay per MB used rather than a fixed monthly amount.
Best for: Light users who want EE coverage without EE prices.
### GiffGaff
GiffGaff runs on O2's network with transparent pricing and a goodybag system that lets you choose your allowance each month. European roaming is included on all plans.
Best for: Users who want flexibility, good coverage and included European roaming.
### ASDA Mobile
ASDA Mobile runs on Vodafone's network and offers some of the cheapest data plans available in the UK. No-frills but the value is hard to beat.
Best for: Budget buyers who want low monthly costs above everything else.
A flagship phone on a 24-month contract typically costs £50–£80 per month including the handset. The same handset bought refurbished plus a SIM only plan typically costs £25–£40 per month total — a saving of £300–£900 over two years.
Refurbished vs new phone — is it worth it? →
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