Good morning Merlot, welcome to the forum. I too hail from QLD and actually live across town from Bundy.
As you say, temps are a bug bear at times, but where there's a will there's a way. Bundy has got himself a great cave set up, which is posted here somewhere, while I, for the moment, am still using the esky.
It you do a search here on UHT milk, you will find that there have been a number of discussions on it. I know my my book says that UHT milk can be used successfully, but I haven't had much luck with it. I have learnt that I would rather pay a little extra for good milk, than throw 10ltr down the drain.
Mungulli milk is an excellent milk. It is pasturised but not homogenised, and they also have a skim milk version. As Cheese head pointed out though, skim will give you a lower yield, so don't get disappointed.
Anyway, great to have you here.