Hi Peter I just found your message when browsing for my (O)Leary. Margaret Leary was born Wexford (county or town) about 1819 (from age & place recorded on death cert).Her father might have been John.She married (presumably) William Dawson about 1839.He was a sapper and miner in the British army, stationed in Ireland. No record of the marriage in England. They had a son William Henry Benjamin baptised at Dungarvan in 1840.After further children born in Lancashire and Woolwich and probably elsewhere, they ended up in South Australia.
A long shot, but can you see any connection with your Wexford Learys?