I have an ABC file of 40 basic Scottish session tunes on my website - they're all ones that are very widely played around Edinburgh, the east coast of Scotland and north-east England.

http://www.campin.me.uk

Further afield they won't be as much use. It would be useful to have something similar for other regions - maybe separate ones for London and the South-East, Midlands and East Anglia, south-west England, Yorkshire and Durham, Wales, the Irish-influenced north-east of England, Glasgow and south-west Scotland, the Highlands.