I used to work at one of those sites - where the Emplacement blocks and gun mounting plates are still visible and the ammo lockers are still intact (lights working) and earth covered.
The 50's control center (GDOC?) for North London is still there too - A concrete theatre, in similar form to the WW2 Ops buildings, with a viewing gallery.
A spooky place to visit when you know what it was supposed to do.