Best bed for waking up aching

I would be very grateful if you can provide advice on the best type of bed and mattress.I have been reading about the Silentnight Geltex beds, but not sure of the best one for us!I am only 4'10.5" and weigh 6st12lb. My husband is 6' and weighs around 12st.We got a new mattress last year; it supposed to be medium firm, and did stop the aches and pains at first, but within a couple of months it started sagging.Every morning we wake up aching all over.We probably need to replace the bed base and the mattress, as the base is a Myers sprung edge which I bought in 1991; so it is quite old.My husband thinks we need a firm mattress, but I'm not convinced.I don't think a foam mattress would be suitable, as he gets too hot in bed as it is.