Here are some links from the fascinating Subterranea Britannica guide to underground Britain. As might be expected, former Middlesex is rich in military bunkers and underground control centres, starting with the former civil defence centre for the former county. This was built in Hatch End in 1943, reactivated in 1952 and remained in use until 1968 (for the last three years after the abolition of Middlesex it was the centre for London Borough of Harrow).
Middlesex’s two regional war room have had contrasting fates. That at Southall is flooded and when visited in 2002 was in the appalling state seen above. The Mill Hill centre, by contrast was Grade 2 listed by English Heritage.Despite this it was converted for sale as an unusual luxury house.
Other bunkers had more wide ranging responsibilities. RAF Uxbridge operations room was the headquarters of No 11Fighter Group, responsible for the defence of South East England. This is now a private museum, part of RAF Uxbridge, which is in the course of being vacated and put up for development. To discuss a visit call the developers, VSM estates . Outranking the rest is Paddock in Dollis Hill, a more secure and less central alternative to the Cabinet War Rooms under Whitehall; Churchill held two meetings of the war cabinet at Paddock.