I bought my double memory foam mattress topper from ebay for about 120 including postage,(it was also 2 day delivery!) and I find it really good, its 3 inches thick. Argos does cheapish toppers (and delivers) and Ikea do cheapish mattresses, my brother bought his from there.
"Before I shaped you in the womb, I knew all about you. Before you saw the light of day, I had holy plans for you" Jeremiah 1:5
HEDS, IBS, Osteoartritis, Bursitis, TMJ, being investigated for fibro, CFS, MPS