The Vispring mattresses are good but very expensive and extremely heavy, so heavy that I couldn’t turn the one I had bought in a sale at Arding & Hobbs, Clapham Junction, before they closed down. I think I paid about £500 for the whole bed as it had been a former display model.
As said above, do have a look at the Dunlopillo beds - they are made of latex, which is very different to memory foam. If they still make them, see if you can find a pillow top version. A friend of mine bought that version. She loves it. Bought from a shop in Bristol. Lots of furniture stores sell Dunlopillo, but evidently not John Lewis anymore. You really need to go round various stores and try out different mattresses. A sprung base also makes a big difference.