The UK's telecoms regulator Ofcom has launched a new interactive tool that will let you check what mobile signal will be like for you whatever network you're on.
Whilst coverage checkers have existed for a while, this is the first time we've seen all four major networks combined in the same one - and backed with the credibility of Ofcom, the organisation that should be looking out for us consumers.
On the web app, you can enter a postcode or a location and choose to filter by network (EE, O2, Vodafone and Three are all listed), as well as the type of signal you need, whether voice calls, 3G or 4G. You can even select whether you're indoors or outdoors.
If you're on one of the UK's MVNO operators, the signal will be the same as the parent network (Wikipedia provides a handy list).
So go give it a try, and next time you switch network be sure to check your coverage on it first.