In reply to Steph-in-the-West:
I got one of these. Goes straight onto a fixed base, no need for a base with extra springs.
It is FAB, have never looked back. Great to sleep on, to have breakfast in bed on, to lounge on and read...to..er...'bounce' on.
The cost is not cheap, but it has a minumum of a ten-year life.
It is actually a high-density foam, with specially sculpted laser-cut blocks and channels that allow the sticky-out bits of you (shoulders, hips, etc) to sink in while the rest remains supported; the channels allow moisture and heat to flow away, thus allowing you to stay non-sweaty in bed (and allows the mattress to air out, thus avoiding the unpleasantness of various small creatures sharing your moist mattress with you!)
There is also an option to have the same mattress wiht a tempur-type foam topper built in.
I found the tempur-foam pillows to be useless- like lying on a brick, once it mouled to shape. I had to chuck mine and go back to a normal pillow.
Sxx