It is probable that the earliest known versions of many of the ballads in Child's great collection can be traced to Scotland (especially the North East) and England, but who knows where they originated?
One of my reasons for contributing an answer to your question is that I believe that some of these traditional performers are in danger of being forgotten. It seems to me that the Irish singers that I mentioned are wonderful singers and I love the way that they sing these ballads in typical Irish styles and, hence, throw new light on them. Something similar happened in America - on Saturday I finally got my hands on the Rounder CD of the West Virginian singer, Texas Gladden - more Child ballads and another different view.
Before I drift completely off the point, may I also suggest that you examine the repertoires of two more Irish geniuses - Paddy Tunney and Packie Manus Byrne - off the top of my head I couldn't tell you how many Child ballads they had/have but I guarantee a wonderful journey of exploration!