Cheapest Unlimited Data in the UK: Where the Real Deals Are

What is the cheapest way to get unlimited data in the UK? Right now, around £12-£15 a month on a SIM-only deal from a smaller network — less than half what the big four charge for the same thing. The catch, as always, is in the details: speed caps, deprioritisation and contract terms that turn a bargain into a regret.

I’ve spent enough time comparing unlimited data deals across the UK to know the headline figures rarely tell the full story. Prices shift between providers, the small print hides the real cost, and what works brilliantly for a mate in Manchester might be a poor fit for a flat in London. So let’s cut through the noise and look at what actually matters. If that’s on your mind too, have a look at our guide to how to set up parental controls on a child’s tablet — it pairs naturally with everything below.

What is the cheapest way to get unlimited data in the UK?

The cheapest genuine unlimited data SIMs come from MVNOs — smaller networks riding on the big four’s masts. iD Mobile, SMARTY, Lebara and Talkmobile regularly offer unlimited data around £12-£16 a month on 12-month contracts, and short-term deals dip to £10. That’s real unlimited data for the price of two coffees.

SMARTY (which runs on Three’s network) is my usual recommendation for bargain hunters: one-month rolling contracts, no credit check drama, and unlimited data around £15 with frequent promotions. The rolling contract is the killer feature — you’re never trapped if a better deal appears.

Now for the part most guides skip: the practical trade-offs. Worth a read alongside this: our guide to how much does a laptop cost for a university student in the uk.

The catches hiding in cheap unlimited deals

The key points, stripped of fluff:

• Speed caps: some cheap ‘unlimited’ plans throttle you to 2-10Mbps — fine for browsing, painful for video. Check the fair-use small print.
• Deprioritisation: MVNO customers can be slowed first when masts are congested. In busy city centres at rush hour, you may notice.
• EU roaming limits: ‘unlimited’ almost never means unlimited abroad — most cap EU roaming at 12-30GB.
• Tethering restrictions: a few plans limit hotspot use even with unlimited phone data.
• Annual price rises: even budget SIMs now include inflation-linked rises; factor in £1-£2 a year.

It’s worth pausing here to think about what you actually need versus what sounds nice on paper. Providers love selling you headroom you’ll never use.

Do you actually need unlimited?

Be honest about your usage: the average UK mobile user burns through 8-10GB a month. Check your actual usage in your phone’s settings before paying for unlimited — a 30GB SIM at £8 might cover you with room to spare, saving £80+ a year.

Unlimited makes sense if you tether a laptop regularly, stream hours of video on commutes, or use your phone as home broadband backup. For everyone else, it’s often peace of mind you’re overpaying for. There’s no prize for buying data you never touch.

How to switch and keep your number

Do it in this sequence and you won’t miss anything important:

1. Find your PAC code: text PAC to 65075 from your current SIM — it’s free and arrives in minutes.
2. Order the new SIM online; it usually arrives in 1-2 working days.
3. Activate the new SIM and give them your PAC during signup — your number moves over, typically next working day.
4. Don’t cancel the old contract yourself; the PAC transfer closes it automatically.
5. Check your old contract isn’t still in term — early exit fees can wipe out a year’s savings.

Quick answers

What’s the biggest mistake people make with unlimited data deals?

Rushing in without comparing options. Most people grab the first unlimited data deals deal they see — usually an advert or a mate’s recommendation — and never check whether it actually fits their situation. Spend an hour comparing two or three alternatives, read the small print on the cheapest one, and you’ll dodge the regret that lands three months later when the bills arrive or the limitations start to bite.

How long does sorting out unlimited data deals usually take?

Less time than you’re probably imagining. The research takes an evening, the decision takes a day of mulling over, and the actual doing is usually under two hours. What stretches it into weeks is dithering — half-decided, tab-hoarding limbo. Pick a deadline, gather the facts from this guide, make the call, and move on. Done beats perfect here, every single time.

Can I handle unlimited data deals myself, or do I need professional help?

It depends on complexity and stakes. Straightforward unlimited data deals tasks are well within DIY territory with a decent guide — most people manage fine and save a packet. But when money, legal compliance or safety are involved, professional help pays for itself quickly. My rule of thumb: DIY when the worst case is a wasted afternoon; call in a pro when the worst case is wasted money or a legal headache.

Pro tip: whatever you decide about unlimited data deals, set a calendar reminder to review it in a year’s time. Prices, products and your own needs all shift — the people who get the best value long-term are the ones who revisit decisions, not the ones who choose perfectly on day one.

My honest take

£12-£16 a month from SMARTY, iD Mobile or Lebara is the cheapest genuine unlimited data in the UK right now — but check you actually need unlimited first, and read the speed-cap small print before you commit.

At the end of the day, the right choice is the one that fits your life and your budget — not the one with the flashiest advert. You’ve now got the facts; trust your judgement. And do me a favour — once you’ve decided, tell a friend. Half the country is overpaying for unlimited data deals simply because nobody talks about it. For the official word, see Ofcom: switching mobile provider. MoneySavingExpert cheap SIM guide is also worth a look for independent comparisons. And if you’re still weighing things up, our guide to which is better for streaming in the uk netflix or disney plus covers the next question most people ask.