"I got Becket's The Mowing Match and Drinking from the file and have been singing them for years"

That's interesting, Jim. Harry Boardman sang 'Drinking' and attributed it to Beckett W. via MacColl, but I've seen no other reference to it beyond that. So it may have been part of that BBC programme, then...

"MacColl's tune is virtually the same as Frank Kidson's Whittingham Fair"

Do you mean the 'Whit Fair' in Bruce & Stokoe? All the Kidson versions of 'Scarborough Fair' that I can find are major, but the B&S tune is modal, and I've thought before that it was the nearest trad tune to the MacColl one.

Personally I think his tune for 'Four Loom Weaver' is a magnificent match of words and melody, and I have no objection to him having done it - if indeed he did. I just like to tease out the sometimes tangled histories of as many of these revival favourites as possible.