winter housing

Have had our rabbit since march this year, am not sure how old he is but would guess maybe about a year old by now.
As winter is almost upon us here in the UK, my wife is a little worried if he will be warm enough in its hutch of a night. He spends most of the day and the early evening either running free in the garden or in the house and has always been 'reluctant' to go into his hutch of a night-time - - - the weather getting cold now I can understand. The hutch is a well built affair which we cover up with a water-proof sheet of a night. Will he be warm enough in this during any cold weather ? I can make room, at a push, in my shed for the really bad parts of the winter if needed. My wife has suggested putting a hot-water bottle in there with him - - - -is this spoiling him ?
Grateful for any advice here.

[Joanne]

I would put him in the shed at night it gets very cold mine are kept in a garage with a nice thick blanket over the hutch to keep them warm. I would not put a hot water bottle in if he can get near it he could burn himself .You can get a thing called vet bed you can buy it here www.bunnybazaar.co.uk also put a sock over the water bottle this will stop it from freezing . Also I put a layer of Russell rabbit chopped hay from wilkos down and cover it with wood shavings in the living side of the hutch to keep them warm. And be careful with grass when it freezers at night and the rabbit eats it in the morning it can make them very ill.