Thanks for your question and providing your body height and weight.
Based on the body weights you have provided, you would require a medium spring tension. The spring unit is there to support your body weight and it subjectively decided by your body weight.
|Upto 8 Stone / 50kg||Soft
|8-16 Stone / 50-101kg||Medium
|16 Stone / 101kg Upwards||Firm
From there your personal preference in the comfort layer and your sleeping habits will determine which mattress to go for. As you are a back and side sleeper that is suffering from back pain. This would suggest to me that the mattress you are using it too firm. Especially if you are still experiencing this with a memory foam topper.
I would advise having a look at the Origins Pocket 1500 or the Artisan Naturals.
The Origins Pocket 1500 is the best selling mattress in our synthetic fibre range and is a medium in the comfort layer. This would provide you with the right amount of sink in the upper layer whilst still supporting you with the 1500 pocket springs. This is a two-sided mattress that carries a 3-year guarantee
The Artisan Naturals is 85% natural fibre mattress and is a medium in the comfort layer also. The spring unit in the Artisan Naturals is a handmade calico encased pocket spring designed to independently support the body weight of the sleeper(s). With this mattress being 85% natural fibre it will provide a cooler sleep surface than a synthetic fibre mattress/memory foam. This is a two-sided mattress that carries a ten-year guarantee.
I hope this helps, if you have any further questions please don’t hesitate to contact the office on 0161 437 4419