Although not a Folk Club and simply a pub,the Twa Tams in Perth could be included in the list as it has live music on most nights with a great range of genre and not just the usual loud pop/rock bands.
They have blues nights, jazz nights, and even the occasional swing night. Lots of Folkies attend the Open Mic on a Sunday afternoon. There is a Trading session on a Monday night.
Mid week between 12.00 and 3.00 there are quiet sets played by very talented singers and musicians.
This is a pub not to be missed.