I think the phrase "19th C music hall racism" is a bit unfair,
Many of the original touring minstrel shows were genuine black performers, several troupes came to England and were extremely popular. I can see no reason why white performers might not copy the black artists by blacking up in order to cash in on a popular music trend, patronising possibly, but not necessarily deliberately racist ( although doubtless there were some bigots who used the opportunity to mock the black artists)
I can also imagine the dancers in the border villages utilising some of the tunes, instruments and black face makeup of this extremely popular entertainment to liven up their otherwise rather simple dance routines.
I have never denied this connection, indeed it seems obvious if you know anything about the tremendous popularity of minstrel shows and there effect on the mainstream popular music of the time.
During my time with Motley Morris we were quite happy to explain this to anyone who asked for information However we saw no reason for giving the rather boring history and geography lesson about every dance, so beloved of Cotswold sides so saw no reason to lecture our audience about what we did, but I repeat The information was freely given to those who enquired.