This is an update to what I know now.
My great grandfather was baptised JAMES McDOWELL on the 5th April 1846 in St Mary's Comber.
His mother was JANE McDOWELL, she was single when he was born.
When he joined the army in 1864 he gave his name as JAMES PATTERSON with his next of kin given as mother JANE (No surname) and his place of birth as Newtownards.
He was married in Colchester in 1876 and gave his father as ROBERT PATTERSON (deceased butcher).
He died in Glasgow in 1915 and the death certificate gives his father as ROBERT PATTERSON (deceased butcher) and his mother as JANE PATTERSON (deceased) maiden name McDOWELL.
I assume that Jane and Robert married after James’ birth but I can find no record of it, nor can I find any record of their deaths, I don’t even know if Robert is James’ natural father, so any help would be much appreciated.