I don't think it matters what format anything is on. 15ips broadcast quality reel to reel would be ideal but I imagine most stuff is on cassette that anybody's recorded. Somebody's got some stuff that they've recorded on cassette by pointing a microphone at the radio from the days when cheap recording hardwear was in it's infancy. It all helps the cause. Singers nights can be just as interesting as guest nights with the diversity of styles that they generate. Remember I don't want a copy, just the details of what you have then I can get back to the BBC to see if they would be interested in.

Keep looking.