If you're a regular changer then get a Hostelling International membership (YHA in australia - $60 or something per year) and then use Travelex. Wave the card and hooray - no commission. Sometimes you need to demonstrate to the Travelex people which buttons they need to push on their computers but they always come around.
Sending money between accounts (Oz, NZ & UK) works well with a company called tranzfers - it was 7GBP last time I used the service. If you pm me your email, I'll get you a reference (personal plug here - if I sign you up I get a free transfer).
UTR