The 100TU does not have that good of battery life. Its battery life is the same as my 15.4" 2.0ghz C2D Toshiba laptop.
The Samsung NC10 has the longest battery life. Around 6 and a half hours of constant use. It also has a 160gb hard drive with some other netbooks don't even offer.
However, Samsung does not sell laptops to Australia. So if you decide on the NC10 (Which is my number one choice) You are looking at buying it from an overseas company that can ship to Australia, or off of Ebay.
My next choice after that would be the MSI U120 or U100. Both great netbooks.