P.S. Thanks, Gerry, for the author's name!

The group Garva recorded it on "Sweet Liberty". Terry Coyne recorded it on "The Other Side". I have neither CD, and they appear to both be OP. (Out of Pressing?)

I found this on Google from IRTRAD-L:

Hi Philippe,

There exists indeed a song "My Old Man" (...), which I have on an album by Terry Coyne, who
also used to sing this song with the now-defunct band Garva.
he gives it as being "Trad. Arr. Terry Coyne", and in the notes to the song he
mentions that he got it from Maurice Coyle from Coore, Co. Clare, who is a
guitarist and singer himself.

Hope this helps,

Han.
--
Han Speek

But it sounds more modern than trad to me, so I'm sure you must be right that Alistair Hulett wrote it.