You've probably done it anyway, but for those who haven't, this cache is a must do! Found it a month ago though, but never too late to recommend!
GC1782ZWrighty took me to this one after a good series, on the way home, felt a bit scary going down into the bunker, but a well stocked cache, and interesting history.
Also, outside the bunker, were amazing views (for the people who don't want to go down) to enjoy (though the cache is actually inside the bunker, hidden quite well) and the whole thing was topped off by seeing five red kites putting on what seemed like a 'show' - amazing.
So, yes, something unique and different, never done something quite like it before!
Check out this photo Wrighty took of me coming out of the bunker: