I'm not sure about this series either!
What has annoyed me is they have referred to the 1939 as a Census. Surely the professionals who work in the offices of the various companies know that is not correct.
Wouldn't be a bad idea if they explained what the 1939 survey was, and its purpose. I understand it was used for the issue of ration books at the start of WW2, and later for the issue of National Health numbers when the NHS was set up. (1947?)
FS