What a great question! I recently went for an interview at a temping agency, just for some temporary office work and was told that I "Don't look corporate enough" by the rude cow interviewing me. She also mentioned that "The UK is far more casual in work dressing than Australia" and that "South Australia is far more conservative than the UK with regards to dressing for the office" You be the judge of that one eh? Needless to say I shan't be working for her!
That notwithstanding, I am now happily employed within the SA Government at Disability SA and no one here seems to get too uptight about the way anyone dresses. Most people here opt for similar stuff to the UK, trousers, tops, blouses, etc. I reckon as long as you look clean and tidy no one will mind unless you are heading for a really top job in the CBD, (or you happen to go to that particular agency!!).
Best of luck, and I totally agree, shop before you come here and bring a case full of office clothes, (I'm missing M&S). You can buy casual stuff here by the tonne, but not really good workwear and comfortable work shoes, especially if you're not a 'standard' size!