Thanks guys: a few additional snippets there.

There seems to be plenty of info on Patrick Donnelly but nothing definitive (as yet traced) on the origins of the song. I only scratched the surface of the story, seeing only a few secondary sources, for, as John Moulden said, I had to do as best I could in the time available, before dashing off to investigate the next mystery! However I believe that the answer exists. It's just a question of having the time, opportunity and the motivation to go digging deep.                     

Personally, I've never been 100% convinced that the Bard and Donnelly are the same person. This MAY be purely legendary. I know of one scholar near Mullaghbawn (a rather staid fellow, it has to be said) who is outraged at the thought of the good Bishop being linked with the worldly Bard.