"Telling them to pull their finger out" won't achieve anything except to piss the person opening your letter off.
However, making some polite but firm enquiries would be totally fine.
The main thing to keep in mind is that the RAAF is like any large organisation -when you make contact with it, you may not be talking to someone who knows, or cares about, the answer to your question.
Some tenacity is needed, plus careful noting of who you talked to, what their position is, and what they said.
If someone fobs you off with something non-committal like "You'll be contacted in due course", try to pin them down to something specific. If they can't tell you, ask for the contact details of someone who can, then send a letter or email to that person.
Putting things in writing is good, or at least keeping your emails or records of phone conversations so if someone says "Try us again in a month", or some such thing, you can come back to them with specific dates, times, who it was, what they said, etc., so as to not let them use the same excuse twice.
Good luck and keep trying, and don't be put off by the bureaucracy.