Brannan family ancestry

I am searching for information about the ancestors of my great great grandfather John Brannan (sometimes spelled Brannon) who married Bridget Henry in Newcastle upon Tyne in 1841.

From the marriage certificate and subsequent documentation we know that he was born around 1823 in Ireland. His parents were John Brannan and Martha (Unknown) and that he had a brother James and either a sister or sister in law called Jane.

In Newcastle he worked as a Labourer in the Walker Ironworks until he died. Both he and his wife Bridget were illiterate.

The problem we have is that we do not know where he was born in Ireland. Some family members think it was Ballycarran, some Roscommon, some Fermanagh, some Maghera!

Finally there are some family stories that his father might have been a soldier.

All information, hints, tips, ideas, clues indeed ANYTHING gratefully received!