This thread seems a suitable place to mention the Singer/Song/Sources articles in the Autumn 2012 English Dance & Song. Derek Schofield explores the complex ancestry of the version recently recorded by Maz O'Connor. He mentions the story that 'Jim Copper had the first verse and Bob completed it from the Gardiner manuscripts' but points out that those manuscripts do not contain the words as sung by Bob, and he quotes Jon Dudley as thinking it "unlikely that Bob searched manuscripts or broadsides at Cecil Sharp House". Derek also points out that the notes to the 4 LP set "A Song for Every Season" state "First verse and tune from Jim Copper (from his father), rest of words from Folk magazine, No. 1".
So we already have two conflicting accounts of where Bob got the other verses.
I can add one snippet. I recall Bob recounting that he got fed up with Jim singing the single verse over and over and therefore went and found the other verses. I think I heard Bob tell that story, but I might have read it in one of his books. Anyway, associated with that story in my mind is a statement from someone (possibly Bob himself or possibly someone else) that he got the other verses from an American version.