Don't know about the latter, Dick! but just interested in why such rules are made- it seems exceptions can be made, which I didn't know! I once asked if Margaret Barry would have been allowed to play her banjo, without a proper answer, but maybe she'd have been an exception?
I've met a few British singers who've come across the same rule, and said no.

I think such restrictions on material as applied at the Singers club and the Newcastle 'Bridge' club were maybe justified in the sixties but why now?