"the overwhelming evidence is that the majority of singers learnt these songs in their youth and were being recorded in their final few years. Singers with only a few songs would easily recall where they got them but I would be more doubtful of those singers with large repertoires who had learnt them from several sources, print included..."

Steve, I respect your experience as a collector, but I still don't buy the idea that those singers were forgetful old dodderers who had only a vague notion of where they got their songs. Childhood memories are very persistent in elderly people, even those suffering from dementia. Cyril Poacher, for one, was quite definite about precisely which songs he'd learned from his grandfather. I take the point that information regarding the generation above the grandparents' is likely to be second-hand and possibly less reliable, but in general the singers themselves are the best and often the only witnesses we have. Some - like the Mr. Hill of Tetford, Lincs., that Fred Hamer recorded - provided accounts of buying, and learning from, broadsides. But most of the singers' biographies that I've read stress the importance of family first, and peers or workmates second, as sources for repertoire. I think those accounts need to be taken seriously.