My grandad (93) says he is tired 24/7, won’t leave the bed except for the bathroom, won’t eat and drinks very little. Always asleep. Advice?

Sounds like he may be ready to move on from this life to the next, so I would recommend getting hospice involved ay this point, as they can be a big help in such a time as this.
When a person is nearing death, they will stop eating and drinking, and will sleep most of the day. That is all part of the dying process, so again, best to get hospice involved.

He's winding down, which is his right.

Can you get hospice in to help?