This is really interesting. I confess I'd never heard of 'Fause Foodrage', given as the original Willie o Winsbury tune. It can be found, apparently, in The Song Repertoire of Amelia and Jane Harris, usually known as the Harris MS. I saw a scanned page of this and it is the same tune. I didn't have this but I've just found a few copies on Abebooks and Amazon - I've just ordered a copy. There's another tune for Fause Foodrage in Christie's Ballad Airs, but apart from the last line, it bears little resemblance to the WoW tune.

'Twas ever thus: the 'folk' use the same tune for different words, the same words set to different tunes and so on.