Its available through the normal Ampthill AC ticket, but requires the syndicate ticket to enable you to night fish.
The pit is over 260 acres, has a stock of around 200 carp, and apparently holds some lovely originals, 70 percent commons, 30 percent mirrors.
Its not something I plan to target any time soon, but definately in the future as my first larger carp water that will take a couple of years (at least) to get to know the basics.
The advantage about it being fairly close is that I would be able to spend plenty of time there. I'll definately be getting myself down there some time soon to have a wonder about.