This is a post I made on the Very British Civil Forum: ARBM War Room.
It is quite amazing what stuff exists in the archives.
The 1933 Census was one of my primary documents for writing ARBM. I considered a Census in the year I was writing about a lucky coincidence. (Shelldrake generously posted the link to the PDF. 1933 Census He has made a number of interesting posts recently that are well worth reading. VBCForum: ARBM War Room )
The Australian and State yearbooks are particularly interesting if you want to know everything from population distribution to exports and imports for an area. Here is the link to the 1934 Yearbook. 1934 Australian Yearbook. From here you can also get access to the state's yearbooks, except for SA and TAS who didn't produce them till more recently.
If you want to uncover information about the various factions, and probably discover more, then a trawl of the Australian archives provides a vast amount of material collected by the Attorney Generals Department: Investigations Branch and the organisations they morphed into. (The Commonwealth Security Service in 1941 and later Australian Security Intelligence Organisation, aka ASIO in 1949) The files hold official correspondence, surveillance reports, newspaper clippings, etc. Some of which is still redacted, more due to the files being scans of the original paper file rather than being classified. These files provided an insight into the numerous factions that existed at the time and were my primary source for factions presented in ARBM. With the exception of the ARC, which I created, all the factions presented really existed and many were under active surveillance.
Here is the link to the National Archive: National Archives of Australia If you start by searching on a faction from the book you are interested in you should find something. The New Guard and CPA (Communist Party of Australia) information is voluminous and will provide many nuggets.
The Newspaper archives are also useful if you know what you are looking for. I generally use Trove at the National Library of Australia. Trove