I can't see a problem with an English folk music degree if it focuses on the styls of music within England. For this to be thorough it would naturally have to acknowledge and highlight aspects of cross-pollenation, history, immigration etc.

It doesn't have to suggest there is a homogenous folk music in England. It might include things like bell-ringing (not just English, of course), pipes, diasporic musics (Scots, Jewish, Reggae etc).

If you look at the Finnish folk scene you find many of the musicians studied at the folk department of the Sibellius academy but there's nothing homognous about the Finnish sound(s).