I believe memory foam is rather hot and sweaty. I was tempted to get one and then when they said it would be hot, I thought, no, as I don't want to be hot in bed. Hope this helps.
Do you need a new bed or just a mattress.
By the way tenrec you have given me that much material in your post it's unbelievable, good job I am a Gentleman though lol.
Ikea will actually give you a 90-day mattress trial, which is more than most shops will. (Though you don't get your money back, you just get to choose another one.) Everyone else expects you to choose a mattress on which you'll spend a third of your life after lying down in a shop for three minutes.
A Tempur matress was suggested to me for back pain. I didn't get one at the time. If you are registered disabled, I was told you don't have to pay the VAT but they are quite expensive. It may be something I will look into next time.
The best advice I can offer is when shopping for a new bed and mattress, take your own pillows from home with you. Spend a good fifteen minutes on the mattress with your pillows and your sleeping partner, and you will get a good idea whether you find it comfortable or not.
If you do your homework first, you may be able to find a shop online which might be cheaper than buying instore.
You could always try a foam mattress topper . Mine changed my sleeping habits and chronic pain on waking immediately. Needs to be at least 3" tho.and a decent make. My king size cost me £95. Bargain!!!!! X