Matt [Another thing that's just occurred to me is there's not much discussion of the Child ballads, which are a pretty canonical part of folk singing today]
Not that many of the Child Ballads actually were found in oral tradition in England in the late 19th/early 20th century. In fact if you look at the Child Ballads, the 305, not many of these seem to have existed in oral tradition in the British Isles for very long. There are obvious exceptions of course. Many of them were revived by the likes of MacColl, but their claim to substantial oral tradition is very slim. Quite a large portion have only been found in print, most of the Robin Hood ballads for instance.