Sorry to hear this, Chris. My thoughts are with you at this difficult time.
I lost my grandad last year, in a very similar scenario. He, too, suffered with dementia, and it was hard to see how it changed him, it truly was awful. To go from him looking after me when I was young, to me sitting with him, and looking after him when he was gradually getting worse. My worst memory of the whole thing was him crying in the living room, apologising that he'd become a burden to us all. Of course none of us thought this. The best memory (if you can really have one, in such an awful situation) was that he still loved a good shave every day. He used cartridge razors, but he had his brush (cheap Wilkinson boar), and his soap (WS Blue bowl) which he used all the time. When he got really bad in hospital, my mum would go up to help him shave still. He was always making sure he was clean shaven, even when he was in the poorest of health, and very frail.
It was the first close loss in my family, and I certainly don't want to experience it again any time soon.
Sorry to go on. My thought are with you mate.