I have had my Millbrook pocket sprung King Size soft divan (with summer and winter sides) for 10 years but it has always been too soft. I do like a mattress that is not too firm, otherwise I find I am stiff and achy, and used to have a medium/soft. However, This is far too soft and I have back ache every morning, and have started not being able to straighten up when I get out of bed, and have back ache all day. I also can't sit up in bed because it sags too much, and this has always been the case with this bed, not just now. I find that the buttons holding the springs down also dig into me even with a padded mattress protector, and I spend the night tossing and turning to avoid the buttons. I have had other mattresses where I can feel the buttons, and so I am therefore reluctant to buy another sprung mattress. However, I tried a memory foam topper and was far too hot. I really would appreciate your advice as to what I should buy. I am a female, weighing approximately 15 tone, and a side sleeper and sometimes on my back. (I sleep on my own) Also, is it ok to buy just a mattress or do I need a complete new bed?