I wouldn't jump to that 1780 date too fast. In the source, Sharp's 'One Hundred English Folk Songs', it says circa 1780, and that title looks like one for someone's collection of garlands, not a specific garland. Garlands themselves were usually collections, although some were a single long song (or poem, or tale). Only the info about the H. Such broadside is in JFSS #6, (1906) where Sharp first published the tune and the single verse he had collected in 1904 (the rest in '100 English Folk Songs' is from broadsides). I think the reference is likely to be fouled-up, but without knowing where the garland is to be found, or who the publisher was, there's not much that can be done about it.I'm not buying that early date without better evidence.