Heya Stu,
I happen to have a mate that goes 'bunker watching' and visiting other WWII relics, about twice a month, all over Europe. Together with some other blokes, they spend their weekends climbing and crawling into all kinds of old WWII structures.
I'm probably gonna be talking to him lateron today, I'll ask him if he was ever there, and if he knows what's what. I do know he's been on many sites in France.
Fred.
Edit: here's a youtube clip, is that the spot?
http://www.youtube.com/watch?v=BwhYUoRNBYU
There is one of them kinda tilted over at a funny angle.. looks to me as if it got knocked over by a heavy shell that landed right beside it, or something. Just a guess though.