Black dancers were working in London during the eartly 1700's, dancing hornpipes. Also playing fiddles. Presumably singing as well, though I can't recall any references. By the nature of things, we should not expect this to be very well documented, in the early years of black entry into Brotain. My guess is that the influence on the music was substantial, particular on urban dance music(eg London, Bristol, Liverpool etc). But I dont think this will ever be proved. I find it intriguing that a very early hornpipe (of the modern 4/4 kind) was called "Salt Fish and Dumplings", and was extremely popular. That doesnt sound like traditional cockney or Lancashire cookery to me!