... a festival in Yorkshire that cancelled many artists and didnt refund most of those that paid in advance
I dont think a folk club organiser[to my recollection] has ever done such a thing...

I think you have made this point more than once here Dick; & I take it. However, it more than once happened to me, back in the lang-syne when I did FC gigs, that the organiser asked if I would work just for expenses this time, as the turnout was less than usual ~~ a popular movie on telly or whatever, and the door wouldn't cover it. I invariably replied, sorry, his problems were not mine ~~ which were driving all that way with a day job to go back to next day; and I couldn't afford to do that just for fun or ego-trip: whereupon I would produce my copy of the contract I had always made sure to have had signed in two copies, one for each of us. So I would always get the money, but not always with the best of grace.

In my own club, I invariably had the agreed fee ready in an envelope in advance, and handed it to the guest before he had even begun the set. If the door happened not to cover it, that was my problem, not his, & I should have scorned even to mention it.

This is all going back 30-40+ years; but I expect some such still occurs occasionally in some clubs???

~Michael~