I think that American sleeping habits must be different to the british. In American films, they always seem to have the flimsiest of sheets on the bed, instead of a comfy duvet. Also, they don't know about hot water bottles. So I hypothise that Americans keep their bedrooms much hotter at night, than the British do.

Personally, I can't sleep in a hot bedroom. I turn the heating down in the evening so the bedroom is nice and cool by bedtime. And believe there is nothing nicer than snuggling down with under a thick duvet with a hot water bottle. I usually have to kick it out of bed once the required internal temperature has been reached.

GF has been burned badly by hot water bottles twice, though. Once from a leak and once from falling asleep lying on a bottle, when she was suffering from agonising muscle pain from taking statins.

Part of that, I think, is film aesthetics. I for one like my blankets piled high. Part of it is the semi-common use of electric heated blankets, which I suspect are a mostly American thing.

As an aside, Cody's Lab did a cool video a while back showing that filling a bottle with liquid paraffin wax gives a much longer-lasting, more consistent heat source, and can be reused by heating it in a hot water bath. The heat of fusion as the wax resolidifies significantly increases the total energy stored and releases it at a more consistent rate.

I have a sheet, a blanket, and a bedspread on top of me. The sheet and blanket are pulled up all the way, but the bedspread is only pulled up to my waist. I get too hot otherwise. My bedroom is the same temperature as the rest of my house. I've never had a need for a hot water bottle.

God bless the Queens Muff Warmer

Does the queen's muff need warming?

He’s dead, so feel free. But I don’t think anybody’s going to be happy with the result.