I think Phil B and Tom Bliss are right. They do exist in the UK. But, under the radar so to speak. Word of mouth seems to be the rule. In 30 odd years, I've done one. At the home of Roger Nicholson (fine appalachian dulcimer player, sadly no longer with us) a double header with Packie Byrne and Bonnie Shaljean. probably about 1978? Very enjoyable it was too. I'm not really gigging anymore, but for a "Pro" musician with a big contacts book, I could see that it could be a great way to fill in the holes in a tour! Even if it was a "pass the hat" event, (plus a bed for the night!) It would be worth it! And a great way to have an informal meet with old friends/fans, who wouldn't bother going to a club. It's just something I've never really done myself.