Hi Maureen, Military records are avaiable here http://discovery.nationalarchives.gov.uk/results/r/8?_q=john%20O%20Connor&_p=1800
Castletownbere is in modern day West Cork.
Christopher Humphrey Connor was born in Boherbee,Tralee 30 Dec 1882
He was baptised in Tralee in 6 Jan 1883, sponsors Humphrey O'Connor & Ellen Flahive.
The Civil Marriage record of John O'Connor & Mary O'Leary is not open yet online but you can order it from the gro.ie (research copy 4 euros) if you wish.
Good luck and do let us know how you get on.