Mattress and base recommendation

Hi I am currently trying to get grips with mattresses as I currently have an ortho pocket sprung mattress and suffer with back pain, I wake up every morning aching all over so feel I need to try a different mattress. I thought I needed a really firm mattress but having tried and nearly bought a Tempur ( could not justify nearly £2000 on a mattress) I am now thinking maybe firm is not so good as the Tempur seemed to do as it said and kept me aligned, although my fear was it would be too hot also. I tend to lie on side or front as does my husband, I like the idea of a mattress that you cannot feel the other one move or get out. Also the bed is a tension wood slatted one, would a divan be better? My weight is 11.5 stone and hubby 13.5. Price wise I would be looking at mid range.