Oh yes, I always thought it unlikely that Martin McDonagh's Irish text was the only example.
Judging from texts of Irish ancestry like "The Faulse Ladye" collected by Phillips Barry:
http://bluegrassmessengers.com/the-faulse-ladye--nelson-nb-c1849-barry-a.aspx
which is similar to the McDonagh text, one gets the impression that the ballad must've had some currency in Ireland.

I wish we'd know more about the ballads that Tom Munnelly collected from Irish Traveller singers.
He mentioned finding Young Hunting several times but none of the texts have ever been published save for McDonagh's version.
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Speaking of Tom Munnelly, I found a tape of the February 1969 recording session with John Reilly in the Goldstein archive.
I thought that might be interesting to you, Jim.

Here is part 1: https://egrove.olemiss.edu/kgreels_unk/218/
And part 2: https://egrove.olemiss.edu/kgreels_unk/219/

I don't know if these are all the songs that were recorded on this occasion, but it is a good number of them.
This was the final recording session with Reilly.
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Now I know nothing about possible ownership of the material issues behind this, but the following ballad may be of interest for your Irish Child Ballad project.
I cut out the long version of "The Well Below The Valley" (Child No. 21) from the tape and put it on youtube for people to listen: https://www.youtube.com/watch?v=O0xZkRSJuBM&fmt=18
Recorded by Tom Munnelly, D. K and E. Wilgus in Boyle, County Roscommon, Ireland on Feb. 22, 1969.

This is not the recording made in Dublin in winter 1967 that was included on the LP "The Bonny Green Tree" (1978) Topic Records - 12T359.
This is a later recording and a more complete text of the ballad. The incest element (as if the story weren't gruesome enough without it) is only found in Reilly's text and foreign analogues of the Mary Magdalen ballad. The Percy text with its exhaustingly elaborate refrain feels like a burlesque, later texts are more serious in tone.

Now this isn't a very likeable song to be honest, it is mostly of historic value. The refrain is also very repetive, I tend to skip it on some verses when I attempt to sing the song. Reilly had more enjoyable songs in his repertoire. I enjoy his take on the "Marrowbones" song, "Tippin' it up to Nancy".

I was also pleased to find that a short bio of John Reilly has been put up on wikipedia: https://en.wikipedia.org/wiki/John_Reilly_(singer)#Biography
The man deserves some recognition for what he left us. One of the finest ballad singers, but then again I could say this about so many of the older Irish singers.
Oh, his Lord Baker/Bateman is glorious. What a wonderful way of giving the tune some variation between verses.

-Kevin W.