It's safe to say Winston is now house-trained. We still shut him in the downstairs bathroom at night, but things have moved along nicely. Up until a week ago I was carrying his increasing bulk down the stairs to the bathroom, as he was reluctant to go. That was obviously a terrible habit to get into, so I changed to coaxing, cajoling and just slightly shoving him with Elf's help. He is now trotting down the stairs happily, right into the bathroom. He seems to be happy to know that that's his place for the night. We still put down newspapers in there, but we have had 5 or 6 dry nights in a row. I think soon we might start to leave the bathroom door open at night so we can go in and use it during the night. I think he will just stay on his bed, hopefully until at least 6am.
He and Hattie mill around together in the kitchen at feeding time and basically ignore each other. Winston actually touched Hattie the other day while he was transfixed by his food bowl being carried past - she turned on him to hiss, then realised that he didn't even know she was there. They regularly get close enough that you can slip between them and pat their furry heads at the same time. A little electrical current runs through you, its kind of special.