I think it's also important to note what Britain was like post-WWII into the early '60s. People were still eating war rations, kids were playing in the rubble of bombed-out buildings (in some areas), and things were rather difficult and bleak for most. There were a handful of TV stations and a handful of state-run radio stations, none of which played much (if any) early rock 'n' roll, and certainly no R&B/blues.

The emergence of pirate radio was the natural reaction to an environment of few choices and overwhelming blandness. Anything that seems forbidden always becomes more attractive to those who seek it out; sure the highly-controlled nature of '50s/early '60s media in the UK only served to make rabid rock/R&B fans out of many Brits. John Lennon, for one, recalled listening to Radio Luxembourg on a clear night, hearing Elvis Presley for the first time, remarking that it was a life-changing experience, without which the Beatles may have never came to be.

When you compare the fairly spartan conditions of the UK with the affluence (and all the distractions of relative wealth) of the US and it's not difficult to speculate why there was such a surge in accomplished musicians from the UK for many years.

And then there was the matter of conscription ending. Young men were no longer obligated to spend years in the military. They went to art schools, moved to Europe, listened to more music. This must have also cultivated openness and exposed young people to culture they may not have known otherwise.