The mysterious extra lines were added by Stephen Sedley, in his book The Seeds of Love (Essex Music, 1967).  He commented:

"Based on the version sung by Ann Briggs on the Topic LP The Iron Muse, which in turn is closely based on the set supplied to A.L. Lloyd for inclusion in Come All Ye Bold Miners by J.T. Huxtable, a Workington collier.  The final stanza has been collated with the mostly garbled text published by Robert Anderson in Ballads in the Cumberland Dialect (1808)."

Almost everybody I have heard sing this song (including Dick and Kate) has used the Huxtable/Lloyd set; the Sedley collation appears on a number of websites, which as usual credit no sources; all but one have clearly just copied it from somebody else's site.