New bed and mattress recommendation

Hi. Husband 5ft 11. 12.9 stone with bad knee and back (biker) I am 5ft 8. Around 10st 7. But usually 9st 12?. I have a slight curvature of my spine and sleep on my side always otherwise it hurts my spine. However I turn a lot too. We both hate foam as find them to hot. We often sleep in the middle together, but separate when husband gets too warm. Current old mattress on floor as had an iron slatted bed frame that broke. Love mattress on floor so presumably mattress now too soft! It sinks in the middle so must be replaced and require a bed frame.