3's coverage is made up of
two kinds of service area, a rapidly expanding video service area which
increasingly covers many of the cities, major towns and motorways in
the UK , and a national voice & picture service area.
When you're in our video service area you can use all of 3's services.
When you are outside our video service you will still be able to make
voice calls, send text messages and listen to email from pretty much
everywhere in the UK using our voice and picture network. Depending on
the handset you choose you can also get access to some of 3's other
services in a voice and picture service area.
http://www.three.co.uk/personal/coverage_/index.omp
