SIM-only deals are the smartest way to pay for mobile airtime if you already own your phone. Prices change frequently, so rather than listing specific deals that will quickly become outdated, here is how to evaluate any SIM-only deal and find the best for your needs.
SIM-Only Price Benchmarks (2026)
These are realistic ranges — the market moves, but these give you a guide for what represents good value:
| Data allowance | Monthly rolling | 12-month contract |
|---|---|---|
| 1–5GB | £4–£8 | £3–£6 |
| 5–15GB | £6–£12 | £5–£10 |
| 15–30GB | £8–£15 | £7–£13 |
| Unlimited (standard speed) | £12–£20 | £10–£18 |
| Unlimited (5G, premium) | £18–£30 | £15–£25 |
If you’re paying significantly above these ranges, you’re overpaying.
How to Find the Best Deal
Step 1 — Check your actual data usage iPhone: Settings → Mobile Data. Android: Settings → Network → Data Usage. Look at the last 3 months and identify your typical monthly usage. Round up — you don’t want to keep going over your allowance.
Step 2 — Check coverage at your home and work Use the Ofcom coverage checker (checker.ofcom.org.uk) to see which networks have 4G and 5G coverage at your key locations. Don’t buy a SIM for a network with poor coverage where you spend most time.
Step 3 — Decide: rolling or 12-month Monthly rolling gives flexibility; 12-month gives a lower price. For most people, 12-month is the right balance — SIM-only deals don’t typically change enough in a year to make rolling worth the premium.
Step 4 — Compare at a comparison site Use a comparison site with real-time pricing (not cached deals). Sort by price for your chosen data amount and contract length. Check the comparison site’s panel is comprehensive.
Step 5 — Get your PAC before signing up Text “PAC” to 65075 (free). You’ll receive your PAC within 1 working day. Provide it to your new provider when signing up — your number will transfer automatically.
MVNOs vs Main Networks
MVNOs (Mobile Virtual Network Operators) are smaller brands that use the infrastructure of a main network. Examples:
- Smarty, iD Mobile: use Three’s network
- Sky Mobile: uses O2’s network
- Tesco Mobile, Lebara: use O2’s network
- BT Mobile: uses EE’s network
- Virgin Mobile: uses O2’s network
MVNOs often have better prices than the main brand but the same underlying coverage. The trade-off is sometimes less customer support capability. For SIM-only, where customer interactions are minimal, MVNOs are usually excellent value.
The Main Networks — What You Should Know
Before comparing SIM-only deals, it helps to understand the four UK mobile networks and their key differences. All other SIM providers (MVNOs) piggyback on one of these four.
EE
EE has the UK’s most extensive 4G and 5G network by coverage. It is the best choice if you travel to rural areas or need the most reliable indoor signal. Plans tend to be priced at a slight premium over competitors, but the network quality generally justifies it. BT Mobile uses EE’s infrastructure.
Good for: Rural coverage, frequent travel, reliable signal above all else.
O2
O2 has strong urban coverage and runs the popular O2 Priority app, which offers early access to event tickets and regular freebies. Sky Mobile, Tesco Mobile, and Lebara are among the MVNOs on O2’s network. O2 roaming in the EU was maintained post-Brexit for most plans.
Good for: Urban users, live events fans, people who want EU roaming included.
Three
Three has the most competitive pricing and typically offers the most generous data allowances — particularly for unlimited plans. Smarty and iD Mobile run on Three’s network. Three’s coverage in rural and suburban areas lags behind EE and O2.
Good for: Data-heavy users, city dwellers, unlimited data at low prices.
Vodafone
Vodafone has solid nationwide coverage and regularly offers competitive SIM-only pricing. It also bundles broadband discounts for customers taking both mobile and home broadband.
Good for: Existing Vodafone broadband customers, balanced coverage and price.
MVNOs Worth Considering
| MVNO | Parent network | Best for |
|---|---|---|
| Smarty | Three | Data-heavy users; no annual price rises |
| iD Mobile | Three | Flexible rolling contracts |
| Sky Mobile | O2 | Data rollover (“Piggybank”); EU roaming |
| Tesco Mobile | O2 | Clubcard points on bill; Tesco shoppers |
| Lebara | O2 | International calls to 41 countries included |
| BT Mobile | EE | Existing BT broadband customers (discount) |
MVNOs cannot match their parent network’s customer service scale, but for SIM-only contracts (where you mostly just use the service without needing support), they are often better value than the branded network.
eSIMs — What They Are and Whether to Use One
An eSIM (embedded SIM) is a digital SIM built into your phone — no physical SIM card required. You activate it by scanning a QR code from your new provider. eSIMs are available on all iPhone 14 and later models, and on many recent Android flagship phones (Samsung Galaxy S22+, Google Pixel 7+, and others).
Benefits of eSIM:
- Instant activation — no waiting for a physical SIM to arrive in the post
- Can hold two SIMs simultaneously (dual-SIM) — useful for separating personal and work lines on one phone
- Simpler when switching networks
Check before choosing an eSIM deal: Confirm your phone supports eSIM and is unlocked (not network-locked). If network-locked, contact your current provider — they must unlock it for free.
Family and Multi-SIM Plans
If multiple people in your household use the same network, some providers offer discounts for additional SIMs on the same account:
- EE: Add-ons for family members on the same account at a reduced monthly rate
- Sky Mobile: Family discount applies when two or more SIMs are active on the account
- Vodafone: Multi-SIM discounts available for up to five connections
- Three: Smarty allows multiple SIMs with shared data pools
A family plan can reduce the per-line cost by £2–£8/month versus individual SIMs. Check the comparison on your chosen network’s website.
What to Do If Your Phone Is Network-Locked
If your current handset is locked to a specific network (e.g., bought on contract from EE or O2), you need to unlock it before switching to a SIM from a different network.
How to unlock:
- Contact your current network directly — they are required to provide an unlock code free of charge
- The unlock is usually done remotely and takes 1–3 working days
- For iPhones, the unlock is registered on Apple’s system and you simply insert the new SIM (or activate eSIM)
- For Android phones, you may need to enter an unlock code when the new SIM is inserted
Do not use third-party unlocking services — legitimate unlocking through your provider is free.
Watch Out For
- Annual price rises: Check whether the SIM plan includes in-contract price increases (many do — often CPI+3.9%)
- Roaming charges: If you travel in Europe, check whether your plan includes EU roaming (many do; some don’t)
- Speed throttling on “unlimited”: Some unlimited plans throttle speeds after a certain threshold — check the small print
See SIM-Only vs Phone Contract for the full comparison, and Mobile Roaming Charges UK for travel data costs.