I've never understood the Hot Water Bottle.
The few times I've tried one, at the start, it was so scalding hot you couldn't get close to it.
When it cooled down it became a lump in the bed, that just seemed to be in the way all the time.
Maybe the secret is that I have never tried a furry Hot Water Bottle!
Oh... And Electric Blankets are the work of the devil!
There again, I am the person that sleeps with the window open all year round and never turns on the central heating.