This get's curiouser and curiouser. According to Lesley Nelson's information at her Foggy Dew (2) page
www.contemplator.com/folk4/foggydew.html
she gives the source of tune used by Canon O'Neill as being from a manuscript that had been in the possession of one Kathleen Dallat, which gave Carl Hardebeck as the arranger.
I have not been successful in finding an e-mail address for her, and no e-mail link was found at her Folk Music of England, Ireland, Scotland, Wales and America web site, to see if she could shed some light on this.