Good on you, Dan - you seem to be very well motivated and have a clue or two, factors which are half the battle.
As has been mentioned above, previous flying experience doesn't necessarily translate to success on RAAF pilot courses, and can sometimes cause hiccups due to the need to 'unlearn' undesirable habits, and possible overconfidence.
There can also be a tendency for significant previous experience to mask learning difficulties until the less familiar parts of the course come up (eg formation, low tactical navigation etc), at which point some people come unstuck.
Just approach it with quiet confidence and you'll most likely be fine.
For what it's worth, I started out in the RAAF as an 18 year old with lots of interest in flying but negligible practical experience (apart from aeromodelling) due to coming from a family not exactly flush for cash, but got through without too many dramas and went on to a reasonably long flying career in the service, so I know it can be done. Lots of other people have too.