Barry, thanks for your reply (& attempt at finding out about James's heritage).
James Aldridge was born 1853 Hurstpierpoint. On the 1861 census he is shown living there with head of house William and wife Sophia, but the ages suggest he was their grandson. I have reason to believe his mother was their daughter Ellen (b. abt 1831), who emigrated to the US in 1853.
He changed his name frequently, so this has proven to be more than a challenge in my research.
His first-born son was my great-grandfather, born Oldham 1874. On the birth certificate James Aldridge calls himself HENRY JAMES HAYDEN and named his son the same. (The mother is named as Martha Caroline formerly Wilkinson b. Middx, but I can't find a marriage for them. She marries someone else in 1883 & calls herself 'Spinster; I don't believe she and James Aldridge ever married). In 1881 he is calling himself HENRY HART (when living with his family in Brighton) and in 1891 he is living in Wales with his two sons and calling himself HENRY JAMES ALDRIDGE. In1901 he is in Knaphill, Woking, again under the name HENRY J ALDRIDGE. It appears he died between 1901 and 1903, but I haven't found a death for him yet.
The name changes certainly don't help, but having found him on the 1871 census as a Soldier, I wondered where I might find his military number and records - no luck so far with a quick search on Ancestry and was hoping to narrow down the field a bit!
Talk in the family suggested my great-grandfather was an army deserter (he served as a Painter for the Royal Engineers at Home from 1915-17 aged 39-41yrs), but records show he was discharged medically unfit for service. My thought is that his father James Aldridge/Henry James Hayden was the actual deserter - did he and Martha run off to Oldham for the birth of their first son, and is that why he changed his name?