Funny thing, coincidence.
I was looking at the `subbrit` sit today myself. My father-in-law has an old ROC (Royal Observer Corps) observation post on some land he owns and I was checking a couple of details about it.
The observation posts are all over the country, so there`s probably still one near you (although many have been demolished/filled in). To find out, just go here and select `advanced search` on the left - put in the name of your town/village and see what comes up.