Which network is my SIM Only deal really on? EE, Vodafone, O2 or Three?

Plusnet, GiffGaff, BT Mobile, Virgin, iD Mobile – with over 20 UK mobile networks to get your SIM Only deal from, choosing between them can be a daunting prospect.

Luckily, things aren’t as complicated as they first appear.

There are only four actual mobile phone networks in the UK, so if you’re keeping your phone and going for a SIM Only deal you’ll be using one of EE, O2, Vodafone or Three.

These are the Mobile Network Operators (MNOs), typically nicknamed “the Big Four”.

These four network buy wireless frequencies from the government, build mobile phone masts and maintain the infrastructure that everyone else uses.

All the other networks, from Tesco to giffgaff, piggyback on the mobile signals of one of these four and don’t actually own any of the network themselves.

These are known as Mobile Virtual Network Operators (MVNOs).

So if you choose a SIM with Virgin, Plusnet, BT or EE – they all use EE’s signal.

Similarly, giffgaff, Sky and Tesco Mobile are all use O2’s network.

Because coverage varies so wildly between different areas of the UK, you need to make sure you’re getting the network you want.

You can check whether your new SIM will support 4G or is only able to get 3G – just tap or mouse-over any of the coloured segments.

Coverage

Knowing which of the Big Four has the best coverage in your area will make it significantly easier to choose from one of the many MVNOs.

The regulator Ofcom has a good Mobile and Broadband coverage map here, and we’d also recommend the OpenSignal app as its wireless coverage is sourced from users themselves.

Because each of the Big Four has at least 97 percent coverage in the UK, it’s very likely that you’ll be receiving equal coverage from all four – and hence all 20 or so MNVOs.

What’s the real difference?

An MVNO might piggyback on the Big Four’s signal, but their pricing and customer service are entirely their own.

For many people, these factors are more important than just raw coverage.

However, it’s still good to know which network your shiny new SIM is going to be on – imagine switching from Three to iD Mobile due to poor coverage, only to later realise that their services are identical?