Frodsham AAOR is one of the most intact AAOR's still standing, but is however up for sale AFAIK. Its last use was as a training/lecture room for Cheshire County Council. I have a had a couple of guided tours by the emergency planning officer, who was a very interesting chap, having info of all the local Government office bunkers.
There are still a few remaining pointers to its former use, such as original room names on the doors and the original forced air system is still in place. Even the original Arials were still standing in the mid eighties.
but mainly it is (was two years ago) full of redundant council office equipment.........