best type of bed

I have a long standing Thoracic spine problem and at night the pain goes into my sides , the pressure of lying on my side in bed seems to make the problem worse so I believe it could be partly down to my mattress a Kozeesleep duchess 1500 pocket spring which is on the firm side. It is also some 7 years old. I am 6ft 2 inches and weigh around 15 stone .I have previously tried Tempur but hated it far too hot. Any advice you could give as to the best type of mattress would be welcomed. Thanks - Alan