andrewh – you haven't said how long you're going for matey, so it's a bit hard to offer any hard and fast advice.
If it's just for a holiday and there's no feasible way of taking the bike as part of your airline luggage, I'd probably look into hiring a bike from one of the many – very good – Canberra bike shops. Importing a bike into Aus as part of a separate shipment is a real hassle, even if sent as fast as possible by very expensive air frieght – and it can take up to 2 weeks just to clear Australian customs. If you're out there for longer, but not permanently, however, I'd definitely recommend buying a bike out there and selling it when you leave.
I took my bike out with me to Aus for 13 months while I was working out there, along with a few other possessions – in the end I think it must've cost around about £1200 total for the round trip – and I was separated from my things for 2 months on the way out and 4 months on the way back! Hmmmm… I wouldn't be doing that again! Hindsight is 20:20 😀