Best SIMs on O2: 20GB for £7.50, 40GB for £8
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We compare the whole SIM only range on O2 to find the ones that come out best in price comparisons with other networks. Last updated: 25th November 2025.
O2's best SIM only deals
The SIM only deal on O2 we rate highest this month
just
£7.50
a month
✔ Unlimited mins and 20GB data See full deal
at o2.co.uk
(opens in new window)
We think O2's best value option on SIM only this November is their discounted £7.50 a month plan below, which comes with 20GB data, plus unlimited minutes and texts on a 12‑month deal:
It's actually possible to beat this deal if you're not fussed whether your SIM is with a provider using the O2 network. But if you are, it is the current best-priced option. Here's where you can beat it on other networks:
O2's 40GB for £8 plan is a good option too
just
£8
a month
✔ Unlimited mins and 40GB data See full deal
at o2.co.uk
(opens in new window)
For those needing more data, we think this discounted 40GB is one of the best SIM only plans on O2 too. It's on a 12‑month deal, comes with unlimited minutes and texts - all for £8 a month:
It might not be the lowest-cost SIM only deal with 40GB data or more on the entire market but if you're sure you need a SIM using the O2 network, it is the best-priced. See lower-priced networks' deals here:
Their £9 for 70GB plan is a decent deal for November
just
£9
a month
✔ Unlimited mins and 70GB data See full deal
at o2.co.uk
(opens in new window)
To get an even bigger data allowance, we also think this discounted £9 O2 SIM is one of their best options. It comes with 70GB data, unlimited minutes and texts on a 12‑month deal:
If you don't need your SIM to be on a provider that uses the O2 network, you can beat this deal elsewhere. But if you do, it's the cheapest 70GB data or more option. Here are other networks you can beat it on:
They're also offering unlimited data for £20 on SIM only currently
just
£20
a month
Increased to: £25.00 on April 1 2027
✔ Unlimited mins and unlimited data See full deal
at o2.co.uk
(opens in new window)
To get an even bigger chunk of data, O2's discounted £24 £20 SIM below is another of their best deals this month. For £20 a month, it offers unlimited data, unlimited minutes and texts on a 24‑month plan:
That £4 monthly saving vs full price will save you £96 in total over the 24 months.
Compared to O2's other deals, this comes out among the best. But it's worth knowing you can get a lower price elsewhere, even on other providers that use the O2 network. See the networks with cheaper plans here:
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O2’s SIM only prices and benefits compared
In our full review of the O2 network we said we liked their brilliant call signal (3G/2G) coverage, their good 5G coverage and their great WiFi hotspot scheme. We also like their WiFi calling and 4G calling.
You have the choice of 1-month, 12-month and 24-month contracts. Their 24-month contracts are usually much cheaper per month, but it’s best to check their current deals for the best possible offer.
O2’s deals tend to be some of the most expensive of all networks, but they’re a bit more competitive on big data deals. There are some smaller providers on O2’s network who offer better value SIM only deals.
They’re also the only main UK network to still offer inclusive EU roaming on all plans. And you can get extras on premium plans, such as subscriptions to entertainment services and worldwide roaming data passes.
Useful link: Read our full O2 review
Other things to know about O2’s SIM only deals
You’ll get your O2 SIM card between 1-4 working days after ordering (depends on your location). And there are premium delivery options too. You’ll receive each size of SIM for any phone. Or you can take an eSIM.
When your SIM arrives, you have 14 days to return it and get a full refund if you’re not satisfied. This will also cancel your contract. Here’s how you do that.
To prevent customers racking up huge bills they can’t pay, O2 make you pass a credit check to join them. If you have a poor or no credit history you can still join O2 on a PAYG monthly bundle instead.
And if you’re switching to O2 from another network you can keep your number by requesting a PAC from your old provider and giving it to O2 at any point. Here’s how you do that.
Useful link: Compare all O2 SIMs