Dan Howdle | May 12th, 2022

How to choose a SIM only deal that's right for you

The UK mobile market is awash with SIM only deals, from the tiniest amount of data to a wealth of unlimited deals. So where do you start when it comes to looking for a new one? If you already have a phone and you’re at the end of your contract, you may decide to stick with your current provider and get a new SIM deal with them, but with so many offers out there it’s always worth taking a look around first.

People using mobile phones

There are several things worth thinking about when choosing a SIM only deal, from which provider has the best coverage in your area to the amount of data you think you’ll need. In this guide we’ve outlined all you need to know when shopping for a new SIM deal, so you can be confident you know exactly what you are looking for.

What is a SIM only deal?

A SIM only deal is where you buy an allowance of data on a SIM card for use in a phone you already have. Whether you have bought a new phone outright and want to find a SIM deal for it, or whether your current handset contract has run out and you are looking to get a cheaper data deal, a SIM only deal is what you will need.

Don’t be put off by the prospect of switching to another provider as it’s simply a question of requesting a PAC code in order to be able to keep your number. If you’ve bought a brand new phone or got hold of one second-hand and this is your first SIM only deal purchase, you’ll have no worries about keeping your number as you will be given a new one with whichever SIM you choose.

Choosing a network and a provider

In this country there are four mobile network operators; namely O2, EE, Three and Vodafone. These are the four companies that own and control the infrastructures that supply us with a mobile signal. As well as the networks themselves, there are a number of what are known as MVNOs (Mobile Virtual Network Operators). These are businesses that rent the network capacity from the network owners in order to provide their own mobile services.

This includes such familiar names as Tesco Mobile (which runs on O2), Asda Mobile (Vodafone), iD Mobile (Three) and Sky Mobile (O2). In some cases, networks own and run their own MVNOs, such as Vodafone, which owns Voxi, Three, which owns Smarty, and O2, which owns giffgaff. BT Mobile is a unique MVNO, in that it actually owns the EE network. Hence all BT’s mobile services run on EE. BT also owns Plusnet, which runs on the EE network too.

Whether you sign up directly with a network or with an MVNO will make no difference to the quality of your connection, and invariably the MVNOs tend to offer cheaper deals than the networks themselves.

Network coverage and speeds

All four networks claim to cover 99% of the population when it comes to 4G services, which will give you pretty reliable connectivity wherever you are, regardless of your network, although inevitably there are some blackspots in certain areas.

According to the most recent report from consumer research group Opensignal, EE still reigns supreme offering the best mobile experience overall – including its 4G download speeds. But when it comes to 5G speeds specifically, Three leads the way, with an average 5G download speed measured of 204.3Mbps, which vastly outstrips the 129.2Mbps of EE, the 100.6Mbps of O2 and the 92Mbps averaged by EE.

All four operators are gradually extending their 5G coverage across the country but it is still primarily limited to towns and cities. According to Opensignal’s research, Three and Vodafone both share the best 5G availability, with EE and O2 trailing behind.

Contract lengths

Most mobile providers offer a choice of one-month, 12-month or 24-month contracts for SIM only deals. Once you’ve decided on how much data you want, if you can commit to a longer contract, you are likely to get a better deal and pay less for the same data than if you chose a contract-free option. On the flip side, if you don’t want to commit, a 30-day deal gives you the flexibility to leave when you want.

How much data do I need?

This is a bit like asking how long is a piece of string, as it really depends on your own situation and how much data you use. Generally, there are three categories of users which we’ve summarised here.

High usage

If you are rarely connected to wifi and constantly use your phone to stream video or audio, then an unlimited data option is likely to be the best choice. As well as giving you all the data you need to play with, it also gives complete peace of mind, knowing that you will never run out and you won’t be charged for any excess usage either.

If you like to be able to tether your phone to a laptop, for example, or if you like to have the option to share data with others, note that these uses of your data are unlikely to be unlimited too. Most unlimited plans come with a limit when it comes to sharing or using your phone as a hotspot, but it’s often in the realm of 100GB, so still plenty for most people’s needs.

Unlimited SIM only deals

Medium usage

If you use your home or work wifi a fair amount, but like the flexibility to use your mobile connection when you want, then you will benefit from a fixed but generous amount of monthly data. If you sometimes find that you need a data connection on a long journey, for example, or if you are intermittently away from wifi, then a chunk of data greater than 11GB but under 100GB should suit.

Most providers tend to offer data amounts in the region of 15GB, 30GB and 60GB, so depending on how much you are away from wifi, and how much streaming you do, one of these will fit the bill. If in doubt, plump for a smaller allowance as you can always increase it if you want to. You cannot, however, lower your monthly amount of data if you sign up to a contract that is for longer than a month.

Compare SIM only deals

Low usage

If you are connected to wifi most of the time, either at home, at work or at someone else’s house, then you will only need a very small amount of data to tide you over on those occasions when you are without wifi.

Some providers still offer minute amounts of data, such as 250MB, but in most cases the entry-level allowance is 1GB. If you feel you need a little more than that, then there are plenty of 5GB and 10GB deals around that should keep you covered.

Data only SIMs

If you are looking for a SIM only deal for a tablet or mobile hotspot device, then there are a number of data only SIMs available. Unlike phone SIMs, these come without a texts or minutes allocation and are designed for getting online when you are away from wifi. As with phone SIMs, data only SIMs come with a choice of data allowances, from 1GB to unlimited, and a choice of contract lengths.

Data only SIM deals

Which providers offer data only SIM deals?

The four main networks – EE, Vodafone, Three and O2 – all offer data SIMs for use in tablets, laptops and MiFi (hotspot) devices. They are also available from several other operators including Smarty, Asda Mobile and iD Mobile.

SIM only providers

Contract SIMs vs PAYG

There are two main advantages to getting a contract SIM rather than going Pay As You Go. The first is that it’s often cheaper – quite simply, you’ll get more data for your money. This is especially the case with top-up SIMs where you just pay for credit on your account when you need it and you are then charged for every minute, text or MB used.

Many providers offer PAYG bundles, which offer better value than top-up and much the same data allowances as a postpaid contract SIM deal, but still quite often at a marginally higher price. You can also set up a direct debit so that your PAYG bundle renews every month if you wish.

The only downside of a contract SIM is that you have to undergo a credit check beforehand, so if you think this might be a problem, then a SIM only PAYG bundle deal is a good alternative.

Frequently asked questions

Can I keep my number with a new SIM only deal?

If you are staying with the same provider then you can keep your number. If you want to switch to a new one , then you will have to request a PAC code from your current provider.

What size SIM do I need?

Most mobile operators will send out a 3-in-1 multiSIM, so you just pop out the size your device requires. Smartphones generally require a nano SIM, as do the majority of tablets and laptops, but it’s wise to check first.

What happens if I run out of data on my SIM?

When you get near your usage limit, your provider will send you a text alert. Your provider will usually block you from using any more data until it renews. You can usually buy bolt-on data but this is expensive. You can choose to set up a spend limit that will allow you to use extra data up to a certain amount, such as £5 or £10.

How do I know how much data I will need?

If you’re not sure how much data to choose, start off with a lower amount as you can always increase it if you need to. Alternatively, try out a one-month contract and use that as a way to benchmark your usage before you sign up to a long contract.