Looking to replace a single mattress

Hi
I'm looking at replacing an old mattress and I read about the following companies that supply mattresses:
Bruno
Eve
Simba
Casper
Reading the information in this forum the mattresses are not that great.
So I'm after something that is more supportive of my back as I weight around 12 - 13 stones and my height is 5ft 10in.
Recently had a lower back problem.
My current mattress is on a single bed (use to be part of a bunk bed) and its on slats.
I was looking at your range of fusion matress's and specifically fusion 3 as a replacement because its breathable and offers
great support has medium tension.
However could you advise?
Many thanks
Jugjit