Findmypast.com and ancestry.com both have the censuses. There are others, but I don't know how good they are.
Best place to start is with what you know. Start with your mother and when she was born and details of her parents. Take it back a generation at a time until you come to Hogan. Once you have details of your maternal grandmother or grandfather, that should lead to your great grandad's marriage cert. That should give an age and thus you can work out when he was born.