Stephen,

For C#, check out the musical traditions website
Musical Traditions

They have a couple of articles by Mike Yates about C#'s collection activities, which I believe has information about individual singers. Also, be skeptical of any statistics you hear about C#'s singers (80% from villages, 20% from towns, for example). Yates has shown that many of the ones used by such critics as Dave Harker are bogus.