It has been a while since I've been there, but try the Lismore located in the WestEnd of Glasgow off Byers Road. I went there a couple of times, I think they have sessions on Monday nights. It was a nice session, mostly instrumental but some songs too, and I was made to feel very welcome. And the repertoire of most of the participants was Irish. Somewhere on the net there is a list of Scottish sessions, but I can't recall the name. You might have better luck posting on www.tradmusic.com , which tends to be a little more "Scot" centric! Good luck.