Recently returned from a quick trip to the UK. First of all, LTE roaming on EE works. However, even with the ability to switch between 4 carriers (EE, vodaphone, o2, 3) coverage was terrible compared to the US. By terrible I mean consistency. Very poor in building coverage, very slow speeds, many periods of no service. Now this was in London and Edinburgh city centers and Manchester was a bit better but in comparison, AT&T in the USA is wonderful!