BBC Tatsfield - Surrey - February 2017
BBC Tatsfield Monitoring station was used from 1929 to 1974 to monitor the frequency of domestic radio broadcasts to ensure the quality and frequency of the signals.
The site was closed in 1974 when its duties were merged into the BBC Crowsley Park site.
The BBC have a nice article with pictures of the site when it was in use.
The buildings that are left are the two at the bottom of the plan. The one of the bottom left is the underground room. The bottom right is the office building.