Looking to change your current data plan to one that better suits your needs? We’re here to help with our round-up of the best SIM deals for May 2025.

SIM-only plans are as they sound – just the SIM without the phone – and they are becoming increasingly popular for many reasons.

These plans offer flexibility by not tying you into a lengthy contract over many years and can be changed readily depending on your needs. They can be even better if you already have a phone you’re happy with, or prefer buying your device outright.

There are many of these on the market, catering for all tastes from unlimited data to 30-day rolling plans, not to mention faster speeds and much more. You can peruse the best SIM deals below, saving you some serious cash on your next network plan.

If you want to pair a smartphone with your newly purchased SIM then you can also check out our breakdowns of the best smartphones, best mid-range phones and the best cheap phones.

Unlimited Data Deals

100GB+ Data Deals

50-100GB Data Deals

10-50GB Data Deals

Below 10GB Data Deals

How to choose the best SIM

There are various factors to think about when considering a SIM-only plan:

Data: Using the phone for streaming, gaming, apps and surfing the web away from Wi-Fi can put a strain on your data allowance. It might be worth looking at your current usage, and seeing what you use or might need in the future when considering an upgrade. It’s always worth giving yourself a data cap that provides some wiggle room in relation to your average usage, just to ensure that you don’t have to incur additional costs if you happen to have a particularly data-heavy month.

Contracts: SIM deals usually have lesser lengths of service than all-in-one phone plans, typically 12-month or 30-day rolling plans, with the latter offering great flexibility. While there are 18-month and even 24-month options available, we recommend opting for a shorter length so that you’re not tied in for long if you’re ever dissatisfied with your service.

Networks: Most mobile phone networks nowadays offer a good coverage area, and it’s worth checking what works best in the usual places you’d be with your mobile. With that said, there are networks that run off the back of the usual EE, O2, Vodafone and Three that offer good service and at a lower price, such as Smarty and Voxi. Some networks also come with additional freebies and rewards services, including O2 Priority and Three Plus, so it’s worth doing a bit of comparison to see what you can get for your money.