Hi Adam, and welcome to the EF from another (former) Sydneysider! Hope you settle in okay when you arrive, not far off now ...
For the social stuff, clearly you need the Social Events section of the forum! Lots of great stuff, to suit whatever you feel like doing!
An extra note on the driver's licence - according to what I found out, changing back to the Australian licence if & when you move back is not a problem, again it will just be a swap ... and if you're a little late in exchanging your licence (ie, over the 12 months) it's not a problem - unless you need to drive in the time between the end of that 12 months and whenever you get around to exchanging your licence.
Robyn, that sounds nasty about the provisional licence!

Lucky I was four years into a five-year licence when I exchanged mine!
Oh, and yes - alcohol is cheaper here. Bizarre being able to get Australian wines cheaper here than in Australia, but that's taxes for you ...