I suppose the radiator could be a little dirty, but the car has barely 20k miles on it - most of it driven in it's first few years of life. I took a quick look at the radiator and there aren't any major obstructions visible, and no bent fins. I also just replaced the thermostat with all of the other service work.
cp1joel keep me posted if/when you diagnose your own situation.
Also, when you said "aus" I thought "Austin" which is where I am but clearly you are on the other side of the world
