DONT PANIC......it is yet another bit of knee jerk legislation which is added to the huge number of new rules and laws tangling up the life of Brits. Evry week I must break at least six laws of some kind or other often without knowing,this one about the taking  of pics is unlikely to make much difference. Since WW1 there have been laws about not taking pics of prisons, war department(now MOD) property and equipment ,but generally these are no longer enforced. I had a good laff when a prosecution was a failure cos someone published a pic of the Post office tower in London. The security services highlighted the role it played in a comms system called Backbone designed to enable cold war bunkers to keep in touch after the bomb.They made a big mess by getting publicity due to the court case.
Nowadays there is a website where you can read all about govt places and it keeps me in the clear for taking my aerial pics http://homepage.ntlworld.com/alan-turnbull/SECRET-BASES/