Ofcom have launched a very useful tool which allows you to see what (if any!), 3G and 4G signal you can get from the main providers across our match.
The Government has signed a new deal with providers which will require them to provide coverage for 90% of the UK by 2017. However the Mobile Coverage Checker shows there is a real difference in coverage across our patch so it is worth seeing if you could get a better service.
Take a look: http://www.ofcom.org.uk/mobile-coverage