Hi Old Grey Whiskers
In addition to what Pat said, you have to tell both Windows and Office
itself to use Australian English.
See
http://homepage.swissonline.ch/cindymeister/LangFmt.htm
In particular, don't forget to check the language of the Keyboard. That's
the one I find is most commonly left to US English.
As a super test, close Word, and re-open it. Create a new document using the
default normal.dot template. Type
Parramata and Marybyrnong. Word should mark both as a mistake, and when you
right-click the words, Word will propose the correct spelling. When you've
achieved that, you know you've succeeded.
Hope this helps.
Shauna Kelly. Microsoft MVP.
http://www.shaunakelly.com/word