"The Singing Englishman" is available free on the web, but it's a very long way from what the original poster was looking for. (It's a gripping read but badly wrong in a lot of ways, which Lloyd himself later acknowledged - his "Folk Song in England" is the updated version).

The Scottish fiddler/singer Brian McNeill has a couple of crime novels that feature folkies - "The Busker" and "To Answer the Peacock". Another Scottish one is Peter Kerr's "Fiddler on the Make".