Thanks anyway Toner.
I really do want to go with the GTM system.
There's an Australian forum
Z Club - Australia's Premier Nissan 370Z and Nissan 350Z Forum where I asked about local experience with GTM and for some reason the responses were predominantly negative.
I find it hard to believe after seeing all of the positive feedback GTM receives by North Americans.
My only other concern is compatibility with RHD cars and how the ECU will work with the system here. But I'm sure that can all be resolved.