Hi Chris, Sorry but I don't have a John Ovenden (so far!) My Ovendens were from Kent & my direct line from Jesse moved to Oxford & branched out from there.
The 1911 census is now available on line (although it is quite expensive), that will give you a little more info given that you know John's wife's name
I don't know how long you've been researching, so sorry if I underestimate you but have you seen your gran's marriage cert? that will give her father's name & possibly a middle name or initial, if he had one, might help narrow him down in other census'. Also, her death cert might help.
Good luck, the chase is half the fun of it 8-) Hilary