Child said "the only English copy of this ballad that approaches completeness is furnished by the Percy manuscript," and it is the only one, outside of a couple of fragments from Scott, included in his popular ballads. Bruce O. posted it in the original thread.

Has any additional information been found?

Bronson shows only the Reilly text.
It does seen a 'wee bit pekuliar' that Reilly came up with a 16-verse text several generations after the Percy MS, and nothing intervening except the scraps from Scott.