Black individuals have, quite obviously, lived in Britain since time immemorial, but as many have pointed out, they have tended to intermarry/interbreed with the general population, thereby avoiding/preventing the development of a distinct Black culture. (Well, at least until recently, when an Afro-Caribbean cummunity and subculture has begun making its presence felt.)

Seems to me, then, that while individual musicians of African descent have undoubtedly made contributions to the ongoing folk process over the centuries, traditional music in Britain has not felt the impact of a thriving African subcuture in the same way that American music has.

As far as musical influences of African origin are concerned, any skilled and sensitive musicians, black or white, who had heard African music could well have felt the influence of what they heard, incorporated it into their playing, and contributed to the ongoing development of the music. Just as with "flamenco the true path," a genre in which guitarists of Spanish, Moorish, mixed and even Anglo-Saxon genetic heritage have long been listening, playing, being influenced, and influencing others.