I think everyone will do their best to answer the question, but it could be a tough one. We will inevitably come back to questions like "What is folk?" and "What do we mean by a Black Briton?"
I used to say glibly that folk songs were just pop songs with whiskers on 'em. I meant that all folk songs started life as the popular songs of the day and just stayed with us a bit longer. I am not claiming that is the right definition, but it helps me get over what I understand by the term.
I think the "traditional British" music now, is a bit of a hybrid and I have several times suggested here that we do not have the continuity or living folk culture which exists in Ireland or in many circles of American music. The effect of Black Britons on various strands of pop music is enormous and almost certainly permanent. I find it hard to say what the impact of any music is on folk music, because I would argue that our folk music has essentially been cut off from a living tradition for so long.
Interesting question.