There was one at a place called the Tap and Spile in Bangor, but I believe it moved years ago. Met a GREAT Welsh fiddler there named Steve. His session mate named Alexander (flute, accordian...that he referred to as 'The Terminator')informed me the aforementioned gentleman was one of the foremost authorities on Welsh traditional music. Another one Monday nights at the Malt Loaf in Conwy. All types of music there from singer-songwriter to trad instrumental.

Also, the Cambrian Folk Society holds one on Tuesday nights at the Cambrian Hotel in Aberystwyth. This is info from a few years back. Things may have changed, obviously.