Mind you, I recently played a slip jig on a mandolin, wanting the usual crew to join in, and the 9/8 floored them, (took years to forget to count and just play on instinct.)

So, the answer is, if you want to play Billy No Mates, stick to slip jigs.

Leadfinger - I don't think there is a norm. or at least, not in the etiquette sense. A folk club will always comprise of those who see reciting songs as something similar to stamp collecting, keeping a record of days gone by in the oral tradition, coupled with those who can play an instrument and realise, quite rightly, that a folk club is an excellent venue in which to share your hobby, those who enjoy listening and / or joining in, and those who are trying to recapture their youth.

Oh, and those who enjoy a pint with good mates.

I reckon you couldn't get a consensus on etiquette from that lot, never mind the other 70% of attendees!