Dear project manager,
I can develop an application written in python, with a graphical user interface (similar to windows), which makes you choose which of your excel files to be used as an input, and outputs a map of Australia showing your data with the representation you prefer. It could be an image, a GIS file suitable to be used in any GIS software, or a map with a complete layout. In principle, the application could be developed so that you can choose each time which kind of representation you want for the map.
The only (minimal) doubt I have is related to Australian postcodes, since I never had to deal with them, since it is the only geographical info, I suppose. I would have to try it with a sample of your data to see how precise results could be.
Let me know if you are interested in my bid,
best regards,
Matteo