Try to find a stockist of Millbrook mattresses.
They're hand made and range in price from £500 up to £2300 for a standard king size, depending on thickness, filling etc.
I have a really bad back problem and tried lots of different beds/mattresses before discovering Millbrook, and finally getting really good sleep, with no backache the following day!
Personally I hate slatted bed bases, I like a deep mattress on a sprung base, it gives better support and a lot more comfort.
Millbrook aren't the cheapest mattresses around, but when you consider how much of your life you spend in bed, and how much better you feel after a really good sleep, they're worth every penny!
I spent what I considered an obscene amount on our bed, but believe me, it's improved my quality of life so much, I'd spend it again in a heartbeat