Choosing the best of both worlds pocket springs with memory foam?

Dear John Ryan
I came across your site whilst searching for the best combination of pocket Spring mattress for myself. I am small build 7 and a half stone in weight and currently sleeping on a Tempur topper on top of a marks and spencer Spring mattress. I do suffer with back & neck pain from disc compression (due to years in the beauty therapy industry) and have found the Tempur quite comfortable in the last 3 years with no overheating problems!
However my back seems to be worse then ever and I am wondering if this combination has been wrong for me.
I have seen a ottoman bed frame with slates that I would like and recently tried out
Which considering it was firm rating 4 I found it very comfortable.
However after reading all your website I am now very unsure.
Please can you advise me on one of your mattresses that compare to the igel Pegasus that would be best suited to my needs.