Evidently the 'poem' appeared in Milton Allan, Songs of the Pendle Country, Book Number 1 (Colne, Lancashire: Joshua Duckworth, 1945). Seven songs, arranged for voice and piano. Since you use the term 'collected', I assume that Brian Osborne got it from somebody's recitation rather than from the book, and so was unaware that it had already been set. It would be interesting to know what the original tune was, and which is the added verse.

Copies come up from time to time in the dealers' lists, and there's one on Ebay at the moment:  Item number: 360128530379: SONGS OF THE PENDLE COUNTRY milton allan