could it be the bed?

Is your bed too warm? Your body temperature drops as you fall asleep, so the bed could feel warmer to you later in the night than it did when you went to bed. Is the weight of the duvet oppressing you? Use a lighter duvet, with a thin blanket handy to add if the night gets cooler. Is the central heating on? Is the window open or closed? Have you had a hot drink not long before going to bed? How long since you ate? Did you watch the TV or a computer screen late in the evening? They are said to stimulate the brain more than reading a book. Experiment with different weights of nightwear, and with none.

Get a notebook and write down all variations of your bedtime routine each night, what the room temperature is, the covers, the ventilation level, everything that you vary. If you get up in the night, note that too. Then first thing in the morning without checking back on all the other notes for the night write down your impression of how well you slept.

Do this for a couple of weeks and then study your notes to see if you can find which combinations were best. Try not to prejudge until you have enough data collected to make sense.

Razzmatazz!

You could try buckwheat pillows. They are pillowcases filled with buckwheat husks and are great for keeping your head cool and can be 'moulded' to fit how you want. It may be worth trying as it would be cheaper than a new mattress! The company is Razzmataz -I'll have to check the spelling! You could just google organic buckwheat pillows and it should pop up. They also trade as Perfect Pillows. I've just bought a new one, they last for years.

Do the sleeping tablets help to get you off to sleep but then you wake up, or are they not working at all now?

Just asked Mr Google and found comparison website. Hope it might help.

www.google.co.uk/amp/www.comparaboo.co.uk/amp/best-cooling-pillows?client=safari

On one of my internet surfings I spotted a pillow designed to keep the user cool. It was intended for cancer patients but hot is hot regardless of the cause, so wonder if this might help you? I'll go and have a quick trawl and see if I can find a link.

Sorry tried that. Have started in one bed determined to stay there but after a few hours tossing and turning getting hot and bothered, I move to the other bed to cool down

How about not starting in one bed and having to move half way through the night? Just choose where you're sleeping either the single or the double and just plain going straight there?

I still get very hot at night and am in the process of trying to find a good pillow - goose feather/down is too soft, others feel like bricks, so I hope there will be some good suggestions on here.

Sorry I can't be helpful but, like you, I have questions not answers.
Although I do fancy one of those 6ft zip-together beds so one doesn't disturb the other turning over etc.

Hi Jordana and welcome to Gransnet

Maybe, a bit like Goldilocks, you are just trying to find out which bed is just right ! Or maybe you are just used to the feel of the double bed? I wouldn't go to the expense of buying another bed though as it probably won't make any difference whatsoever and you will lose even more sleep worrying about the money you have wasted. Sorry I can't offer any advice but from a fellow sufferer, you have my sympathy.