Fair go guys, Australia has only been using metric measure for just over 40 years now.
Same situation for C309a. The ony way around this problem is to create and save your own page setups. and wouldn't you know it, HP does not allow you to save these settings anywhere but in the HP setup so any time you have to reinstall the printer (as I have just had to do) you have to recreate all your own pages again. It was this way with XP and still the same with Win7.
Tech support did not even understand the question when I phoned to ask how could I save the page setups I had created to easily reinstall them after reinstalling the printer.