"We all quite rightly have our specialisms and priorities."
I am of the opinion that there is nowhere near enough and very little that can be downloaded
There is nothing whatever that I can find on how traditional singers regarded their singing and even if there was the more we can get of this gold-dust, the better
As far as the decade of groundbreaking research done by the Critics Group.. you need a bullet-proof vest if you mention anything to do with MacColl   

My intention is to make material accessible in an easily searchable form to those who might not know their way around the scene and don't necessarily want to part of an in-crowd

No, we didn't record any other English singers in this depth - but we did extensively in Ireland and among the Travellers - at greater length with the latter
We do have quite a lot of this type of work done by people like MacColl and Seeger, Charles Parker, Roy Palmer, Lomax and Bob Thomson - all should be invaluable to those wishing to learn about singing
All of this tends to confirm our own work and strengthen my opinion that singers were not the "natural as songbirds" performers they are far-too-often painted
Jim