That was quick, thanks!
I do have that 1833 baptism for Francis Martin in Newry, mother's name Leasery. I did figure that it might be a corruption of Levy/Leavy. That baptism was what lead me to Newry, coupled with an aunt's recollections of a Newry link in the family.
The earliest confirmed record I have is the marriage of Francis Martin in 1865, with both parent's names given, and Peter's occupation, though Francis had moved to Wicklow at that stage.
I was recommended to check the Slaters Commercial Directories, to look for a Peter Martin, carpenter, as a next step. Having found none, or as Shane suggests, not the place to find carpenters, I did a general search across a few websites, and Peter Martin married to Mary Levy turned up on Irishgenealogy, in Dublin.
The options are:
Newry, for which there is a family memory and a possible 1833 baptism for son Francis, but no marriage for a Peter Martin to a Mary Levy/Lea%y,
Dublin, for which there is an 1815 marriage for a Peter Martin to a Mary Levy, but slightly earlier than I would have thought, and no baptism for Francis, or
Wicklow, which is looking quite unlikely.
Anyway, I just threw it up here to see if anyone suggests other avenues which might help to verify anything. Many thanks again.