Doc Roe,the english collector and folklorest, appeared at a fiew festivals talking about Traditional music and song and the performers. It's about four years or so since I last attended one of his workshops but he is still going arround. He has been involved in releasing some of his sound recordings on CD but trying to catch him at a festival would be your best bet. The School Of Scottish Studies in Edinburugh would also be a source of sound recorded material, for study not for sale, and more info on Lizzie Higgins.