The African slave trade with Britain was pretty much non-existent before 1554 so that chances of there being any significant number of Africans in Britain in the 1300s is nil.
I saw the Robin Hood / Kevin Costner shlock movie and sure enough there was a black guy/ muslim hero/ good guy in it, I could not finish watching it. I believe in the 1300’s a moor would not have lasted too long in jolly old England.