Should really only count the population of England as Cardiff and Swansea are only in the English leagues because they are honorary English.
Well, I know Wales has its own league but the football/premier league has admitted them so I am assuming for these purposes that Wales is a part of the premier league catchment area. Not doing so would result in England being underrepresented in its own league!
Apart from Hampshire.
It's hardly a scientific measure of course, it does depend an awful lot where you draw the boundaries! Since the premier league has 20 teams you'd have to divide the country into 20 roughly equally-populated parts to get a truly fair representation. What an odd picture that evokes, a kind of IPL or MLS model with geographically-based franchises; I wonder what the league would look like in that scenario!