Hey Bessie,
I found that a 5cm memory foam/viscogel mattress topper (I spent around £170) on top of a really firm mattress was my sweet spot. Before that, bedtime was something I dreaded because I got such bad pressure pain - and a soft mattress isn't an option because I have back issues. But, I suspect Sunkacola's right - we all seem to experience such different pain symptoms, that the perfect solution for each of us is probably quite tricky to predict. Could be worth experimenting though!
@sunkacola, I meant to ask - did you ever try out a mattress topper in the end? (Or maybe I asked and then forgot....
Not sure!)