I will add another question to Pseudonymous's list. I am not reading the material fast enough to answer it myself.

To what extent was Sharp's search for an English national music a 'nationalistic' one in the sense that that was part of drive in the political subordinate nations of the then UK and to what extent was it a case of appreciating and promoting what was on his doorstep?

Did he also appreciate the national art musics of mainland Europe and the traditional music Scotland and Ireland?

Harker has a theme of bourgoise cultural appropriation of the music of (part of) the prolitariat. It is not hard to find on the internet current examples people being accused of cultural appropration if they play/sing other peoples music and also accusationas of being jingoistic when they play/sing their own. Either way the accusations seem to come from people who, like Harker, have a strong political focus to their view of things.

Happily of course it's not usually like that.