Definitely from travellers in Ireland and Scotland (and England) and from Gypsies in England. I'd recommend the CD sets Here's Luck to a Man and From Puck to Appleby, as well as the CD of the Wiggy Smith family, on Musical Traditions records (www.mustrad.org.uk). But plenty of great singers and musicians were of travelling families: Stewarts of Blairgowrie and Fetterangus, Margaret Barry, Pecker Dunne, Paddy Keenan, etc. Martin Carthy and Norma Waterson and indeed all the Watersons are particularly fond of Gypsy and traveller music. So there is a lot there!