Assuming you both put in an equal amount into the house less your €45k, I dont think it is fair at all.
If you sold the house now for €365k you would still both owe €62k. If you hadn't already put in €45k, that total would be €107k.
So I make it the fair amount he owes is €53.5k.
He may not have that sort of cash up front so maybe you could work out a deal where he pays around 12% of the mortgage to you each month.
I'd get a solicitor involved just to make sure any deal is fair and set in stone..
UPDATE: Looks like Brendan beat me to it