Which? says that among retailers, Dreams, Argos and Bensons for Beds are the WORST and John Lewis and Warren Evans are the best. Ikea are in the middle, but have been improving, and are among the least expensive. The highest rated brand was VI-Spring, but they are expensive. Tempur was 2nd, but you don't want memory foam, so that's not an option for you.
"Earning 71% in our satisfaction survey, Ikea has improved its customer score for the second year in a row, after scoring 56% in 2010 and 63% in 2011. Ikea remains in the bottom half of our table, but is moving up and gaining more positive comments. It's also one of the few brands to get a four-star rating for value for money, along with Marks and Spencer, Millbrook and Sleepeezee."
After years of disappointment with mattresses in the US, we came to the conclusion that price does not equal quality, and none really live up to the hype. Find something you are comfortable with, and plan on changing it more often. And spend a LOT of time actually lying on the mattress in the store, in clothes as near to what you would typically sleep in as possible. Mattresses all feel good initially.