What would you recommend for very different weights and sizes?

I am 5ft 8" and around 10 stones, and my husband is 6ft 4" and 16.5 stones. I have longstanding back issues and need a very supportive mattress (one I can lie on my front and side on as well as my back). I like a firm supportive feel but find our current mattress (A John Lewis Natural Collection 4000 Cotton Medium) too firm (especially for my hip - I have bursistis too) and my husband finds it a bit too soft (he lies on his front and side and is obviously much bigger than me). What mattress would you recommend for us? I'd prefer to steer away from memory foam if possible. Id be really grateful for any advice you might be able to give me. Thanks in advance!