As others have suggested,
(1) Make sure you get a loan car while your car is off the road for diagnosis/repair.
(2) Get a full explanation of the problem(s) and what it will take to repair it, with full estimates as to how long it will take (including waiting for parts from overseas, actual repairs, testing repairs, etc).
(3) Give the dealer/BMW reasonable opportunity to repair the problem(s).
(4) If the same problem recurs, or other major problems surface, then start making noises about the car being a lemon, and ask for either a new car as a replacement or a full refund (whichever you prefer).
(5) If required, write a formal letter of complaint to BMW Australia demanding either a new car as a replacement or a full refund.
The car may be a lemon, but if it's not, at least give them reasonable opportunity to repair it.