I don't know about Clifton's antecedents, but see this earlier discussion: Help: Harry Clifton Songwriter, which includes comments from Steve Gardham, who has been researching him. While it's certainly possible that he may sometimes have "bought in" material, as many performers did (Lannigan's Ball and Rocky Roads to Dublin, both associated with him, were written by D. K. Gavan), I don't think that he'd need Irish connections to write a piece in the style we see in Waterford Boys; "Stage Irish" songs were popular, and any good writer could turn them out. Clifton often set songs to existing tunes, of course.