Interesting pics
http://www.royalsignals.org.uk/photos/rca.htm
The buildings appear to be a ad hoc setup in some ways.... wooden floor . BTW that factory was in the USA , where the sets were made for the British Commonwealth.
You can see the 'RATS NEST" wiring of the 19 set . I am always amazed these sets actually worked. They plonked all the parts onto the chassis in a completely non-methodical way. MIKE