The sites relative to this organisation are reasonably well-documented. However, I am reading a history of the PWE and there is mention of a facility I don't have a record of, at Brondesbury in NW London.
Surprisingly difficult to find any concrete ! information. My guess would be one of the schools in the area - there was a grammar school and a high school, but don't seem to be in Brondesbury but very close. The North-West Suburban plan c.1940 intended to send many government departments to empty schools in this area if Whitehall became untenable. I've had a quick browse at local schools but finished up going round in circles.
Plan A is always more effective when the problem you are working on understands that Plan B will involve the use of dynamite
The following user(s) said Thank You: Richard Austen