My favorite dark sky location near Sydney is on Putty road
Google map link:
https://goo.gl/maps/RjhcwG9idwZwVPhu6
It's around 1 hr 20 mins from my place near Blacktown and the sky is dark, I think it's a bortle 2 and most of the time when I've gone there the seeing has been pretty good.
The 2 problems at this location are that since it is on Putty road there is some traffic on weekends and there can be some dust from cars passing by. Also this location is actually a cafe parking and there are bright neon lights on all night......since it's a free car park where you can stay the night I guess it has to illuminated but it sucks for us astronomers
Another location is this just up the road from the cafe:
https://goo.gl/maps/MRcZ58Pj5XyNteMR6
This is in putty village, there's a little building called putty hall and outside that there is a little parking spot where I setup when I go there. There is only a small bulb here with no other lights around for a few km at least
It's really dark and I've had great seeing here.
I'm sure there are great locations in the south too.....I've been to Helensburgh a few times but the weather there is very fickle......I've had fog come up from nowhere whenever I've gone