Pete - there's a regular bluegrass/Americana session at the Tass in Edinburgh on the first Thursday of the month. There are sessions around Midlothian with a substantial bluegrass/Americana content; PM me for a contact email address.   There is also a regular Americana night (once a month?) at the Eastgate Centre in Peebles. Try http://bluegrassinscotland.com/bgscot/events.htm for more listings, though it's very incomplete - maybe they need help in updating it.