Just to slightly correct Bev and Jerry above, although singing is the raison d'etre of the Goilin club there is not a strict rule on unaccompanied singing, although that is how the majority perform. To quote their own website:

We do not have a ban on musical instruments, but, as its a Singer's club, we prefer, if you want to play that you also sing. Anyone who has an interest in listening to, or performing songs will find that they are "as welcome as the flowers in May".

Certainly on my visit one performer accompanied the song and was later asked to sing another amd the I know that the following weeks guest performer accompanies himself from time to time on concertina.

Don't go there for instrumental sessions though, but definitely go there.