Unlimited Data SIM Deals
Compare unlimited data SIM only deals from Three, O2, EE, Vodafone, and more. Keep your phone, ditch the data worries.
Compare unlimited data SIM only deals from Three, O2, EE, Vodafone, and more. Keep your phone, ditch the data worries.
Why Choose an Unlimited Data SIM Only Deal?
- Heavy streamers: watching Netflix, YouTube, or TikTok on mobile regularly
- Remote workers: using a phone as a hotspot for a laptop
- Commuters: video calls, podcasts, and downloads on the go every day
- Travellers: using data heavily in between Wi-Fi spots
- Anyone who has paid an excess data charge in the last 12 months
Best Unlimited Data SIM Only UK Deals: May 2026
All prices are current as of May 2026. Deals change frequently; compare live on Switch for the most up-to-date rates.
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Do I Actually Need an Unlimited Data SIM?
Unlimited costs more than a fixed data plan. Use this guide to check whether it's the right fit for your usage. To check your actual usage: iPhone → Settings → Mobile Data. Android → Settings → Network → Data Usage.
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What Does Unlimited Data Actually Mean?
- Fair use policies: some networks can slow your speeds if you tether heavily for long periods (usually only relevant above 600GB/month). For standard streaming and hotspot use, you will not hit any limits.
- Speed tiers: some networks sell unlimited at different price points based on download speed rather than data volume. Vodafone offers Unlimited Lite (capped at 2Mbps), standard Unlimited, and Unlimited Max (full speed). Three and EE keep it simpler with a single unlimited tier at full speed. Always check which tier you are looking at before comparing prices.
Fair Use & Tethering Policies by Network
What each major network does on unlimited plans. Most allow normal tethering freely; restrictions only apply to extreme usage.
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Rolling Monthly vs 12-Month Unlimited SIM: Which Is Better?
Two main contract types on unlimited data SIM only UK deals. The right choice depends on how certain you are about staying on the plan.
Rolling 30-Day Plans
Pay month to month with no long-term commitment. Cancel or switch at any time with 30 days' notice. Ideal if you want flexibility or are not sure how long you will need the plan. VOXI, Smarty, and Giffgaff all offer strong rolling unlimited deals starting from £10 to £20 per month.
12 or 24-Month Contracts
Lock in for a fixed period at a lower monthly price than the rolling equivalent. If you leave early, you typically pay the remaining monthly charges. Worth it if you are confident you will stay on the plan. iD Mobile and Three often have competitive fixed deals on unlimited plans.
How to Get an Unlimited Data SIM Only UK Deal
Four simple steps from checking your usage to your new SIM being active.
Check Your Current Usage
Look at your last three bills or check your phone's data usage settings. If you are regularly going over your allowance or paying for data add-ons, unlimited is likely to save you money.
Compare Deals on Switch
Results show every unlimited data SIM only UK deal ranked by monthly cost, including 5G availability, contract length, tethering policy, and roaming terms. Switch compares by actual plan value, not by commission rate.
Keep Your Number (PAC Code)
Text PAC to 65075, free and instant. Give the code to your new network when you sign up and your number moves over automatically within one working day. You do not lose your number at any point.
Receive Your SIM and Start Using It
Most networks post a physical SIM within 1 to 3 working days, or offer an eSIM that activates immediately. Once your SIM arrives, insert it and you are ready to go. No interruption to your service during the switch.
Which Network Has the Best Unlimited Data SIM Only Deal?
- VOXI: cheapest starting price at £10/month on rolling plans. Runs on Vodafone's 5G network.
- Smarty: great value rolling unlimited on Three's network. No annual price hikes advertised.
- Three: no domestic speed caps, broadest 5G coverage outside city centres.
- iD Mobile: competitive 12 and 24-month deals with data rollover.
- Giffgaff: no credit check required. Flexible monthly plans on O2's network.
- O2: Priority extras, entertainment add-ons, strong roaming options.
- Tesco Mobile: competitive pricing on O2's network. Earns Clubcard points.
- Vodafone: speed-tiered plans; Unlimited Max gives full uncapped 5G speed.
- EE: strongest 4G and 5G coverage in the UK, especially in rural areas.
5 Things to Check Before You Sign Up for an Unlimited Data SIM
Coverage
Check the network's 5G and 4G coverage at your home, workplace, and the areas you travel to most. Ofcom's coverage checker or the network's own postcode tool gives the most accurate picture.
Roaming
If you travel abroad, check how much data you can use in your destination country. Some networks cap roaming data at 20 to 25GB per month even on unlimited UK plans.
Tethering
If you plan to use your phone as a hotspot for a laptop or tablet, confirm the network's tethering policy. Most allow it freely, but some have limits.
Price Rises
Some contracts include annual CPI or RPI-linked price increases. Switch flags these clearly. If you want price certainty, look for deals advertised with no in-contract price rises.
Contract Length
A 30-day rolling plan gives maximum flexibility. A 12 or 24-month deal usually saves a few pounds per month. Compare the total cost over the contract, not just the monthly headline figure.
Compare Unlimited Data SIM Only UK Deals Now
Switch compares every unlimited data SIM only UK deal from every major network: no bias, no hidden deals. Results show the real monthly cost, contract length, 5G availability, tethering policy, and any price rise terms. Finding a better deal takes under 5 minutes.
FAQs
What is an unlimited data SIM only deal?
An unlimited data SIM only deal gives you a SIM card with no monthly data cap, plus unlimited calls and texts in most cases. There is no phone included: you use it with a handset you already own. Plans are available on rolling monthly or fixed 12 or 24-month contracts.
Is unlimited data really unlimited?
What is the cheapest unlimited data SIM only UK deal?
Do unlimited SIM plans include 5G?
Can I keep my phone number when switching to an unlimited SIM?
Can I get an unlimited SIM with no credit check?
What happens to my unlimited data if I go abroad?
How long does it take to switch to a new unlimited SIM?
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