another PS
I think I may have found a relevant birth and will try and take that further, although the General Register Office starts their records after that year, so I would have to travel to the Gwent office, as far as I know.
My information has a Catherine as a daughter born in 1829 to Thomas and Hannah, and these parish records here have a Cath as the daughter of Thomas and Hannah but born in 1824 – probably the same Thomas as the ‘builder’ I was looking for, as he is a mason in the parish records.