I have spent ages (and I mean ages) tracking down this place - I was originally told it was within the Castle Hill HAA bunker's grounds, this certainly wasn't the case. So after months of searching and researching, I found my target.
Unfortunately, all that remains are two 'shacks' both full of rubbish, one collapsing. Signs saying private property and the house for the land with very nice vision of the field mixed with the feeling of SERIOUS FAILURE meant I couldnt be bothered to even get out of my car!