There are a lot of conflicts to resolve before this exploration can move forward--UK vs US being a biggie--a lot of what is important in one place is unknown in the other. Played and sung vs recorded is another,   we sang many songs that we never heard on record, and many of my favorite songs on record were never properly rendered "live"--and time of origin is another--with folk songs, many were most popular outside of their decade of origin(or even their century of origin), and of course, there's the "Donovan" issue--he probably inspired more to write, sing, and play, than most of the others, but in retrospect, most would prefer to say they were inspired by Martin Carthy or Doc Watson(who should be on your list above)--