Thank you all for your help. I had a read of the articles and a bit more of a hunt around, and it seems there are quite a few mortgage companies that now loan to over 70s, and older! The house is too small to rent a room out. In a divorce, it is up to the couple to agree on the split of monies, but of course if they can't then they have to go to court, which would cost far too much.
I will have a look into the knotweed for him as well.
Where he lives now is quite a cheap property, I think a retirement flat will probably be more than his house!
Thanks for your help, and please do comment if you have any other ideas!
Last weekend, in Rutland, the first statue in Britain of the late Elizabeth II was unveiled.