I would've recommended hitting up the Cave Clan as they sound basically like the NZ group you described, though you said you're not really into drains so much and they're 95% drain explorers. Not to say that they don't do topsides but most of their activities are associated with drains.
Glad you got to see those 2 spots you mentioned last time you were here as both of them are basically gone now.
Welcome to beautiful Melbourne of course 
Have fun.
Wander often. Wonder always.