As one fellow Aussie to another - I understand completely. Where I am is currently going through a cold patch (Thank God!) but it won't be long before the heat reaches the high thirties/low forties mark again. And I am not looking forward to it.
Hence the reason why I am investing in a window AC as soon as possible. For the moment, though - thanks to Christmas and lack of funds (Thanks a lot Christmas) - I'm making do with a stand fan and trips to the shower every time I dry out. Doesn't help that we're going through a drought and have water restrictions, either.
Might I suggest getting some dark rubber-back curtains to block out all the light, a stand fan with an ice-cold bucket of water beneath it so that as it evaporates it gets blown around the room and wet towels?
Grab one of those long ice-packs (the blue ones) and wrap it in a towel, then drape over unexposed areas of your computer.
Wet a face washer, chuck it in the freezer for a while, then drape it over the back of your fan. Also, wash the fan blades (disassembly required) so that there's no dust on them.
Just a few suggestions. Good luck!