I quite like the Hilton mattresses... having spent large part of my life as a consultant in hotels...

So was pleasantly surprised to see them selling them for the home:
https://www.hiltontohome.com/product...ess-Box-Spring

Standard double mattress, 160cm x 200cm

You could try a boxspring bed if they're available in your area. Or a water bed.

However the problem may be not so much the way bed and mattress are made/constructed, but rather that your backbone gets bent out of shape (or similar) when you're lieing on a standard bed. Without identifying and adressing the underlying cause, the success of any change is at best a matter of luck. A rather expensive lottery if you ask me. If you were more in the northern parts, I'd say to talk to the people from Fanello and have them check your backbone while lieing down. I have no direct experience with them as I have no problem with a standard mattress but two friends would cross the globe for one of theirs as they identified the reason for their sleep problems.

The standard European double is actually 140 cm x 200.

160 cm x 200 cm is a queen in mainland Europe but slightly wider than a US queen. The US queen is similar in size to the UK "king" which is 150 x 200 (the US is between the two). So UK mattresses are smaller than mainland European ones and will be a bit small on many European bed frames. I have the same problem with my UK double which is 135 x 200 and my bed frame which is designed for a 140x 200 mattress.

If one gets a king/superking 180 x 200, then they are all the same. There are other sizes of course but these are the standard ones. I have done so much research over the last month on who has what size, my eyes are crossed!