paulmilbank: I have heard you should avoid Karchers, they have a plastic pump body which is prone to splitting and it is unfixable after it goes. 
The Nilfisk range is supposed to be pretty good with an alloy pump and internals:

the nilfisk package is also available at mitre 10 for $299, with patio cleaner, car brush etc.

I was looking at the K3.170 package from bunnings at the same price, but now leaning towards the nilfisk. 

the karcher had slightly higher PSI, but nilfisk has higher max water flow rate.