Looking for a bit of help, I am currently just under 9 stone; normal weight is around 10.5 stone but i have been rather ill lately. The current mattress I have is a cheap rubbish memory foam mattress which has sunk a great deal all over and has springs sticking in my back at all angles. Would like a mattress that allows me to comfortably sleep on my side, please note I am a bit of a fidgeter in bed also if that helps at all, I also sleep alone and spend a lot of time lying on my back watching tv so would need adequate support for my bad back, although I use a pillow under my legs to help with that slightly. I also have a bad neck and tight shoulders and my sleep position is that of a side sleeper so would also need the correct firmness to allow full decompression of joints so i can wake up without pain or pins and needles. I also hate when mattresses sag and droop/collapse at the sides, very annoying. I initially went to dreams and seemed to like the medium and also the medium firm mattresses, although the medium firm may have been slightly too firm when laid down on my side but much better form when laying on my back compared to the medium. Unfortunately or fortunately, after reading the reviews on Trust pilot I really do not want to purchase a mattress from Dreams in case I hate it and cannot return it, of which most of the bad reviews were complaining about. Anyhow I know this is a long shot but any help and recommendations would be great, your reviews are fantastic online so I am absolutely adamant on purchasing from yourselves. My current dimensions in inches are as follows:
Shoulders - 39
Hips - 29.5
Waist - 29
Would love to hear back from you as soon as possible as I cannot deal with my current mattress much longer, grrrrrrrrrr :(
Few other points:
1. Current mattress is very soft and droops considerably in the middle
2. Looking for a small double size mattress/base/headboard – the whole nine yards.
3. I can not visit a store to test the mattresses directly :(
4. Price range is anything up to £1300ish or maybe a little more if a more suitable mattress is recommended

Thank you in advance and sorry for the ultra-long request :)
Also, I get the feeling at Dreams that they hike the price up and state a massive sale on a mattress that in reality is probably only worth the stated sale price, very disgusting indeed.