I've bought and installed the one linked in Mutley's post. Its an easy enough job, its the whole housing that is replaced, not just the bulb and the light is a LOT brighter - good spread of light across the whole boot.
I've just checked in the dark, unlocked the back and folded the rear seat down and I can't see the light on at all, dim or otherwise so happy days.
Good spend for £8.99 as I use the boot a fair amount at all times. Cheers Mutley for the tip.