Hi Theedmancometh,
RAAF upper age limit is 43, but they have a stated preferrence for 27.5 years old.
See:
http://www.defencejobs.gov.au/default.asp?p=742#403
So far recruiting have said that my age may have an impact on whether the RAAF accept me, but there are no guarantees either way (obviously!) so it comes down to getting the RAAF to understand why they need me instead of some 17y.o. straight out of school.
They've also said that the RAN and the Army won't see my age as a deterrant to entry to those services.
And it was mentioned earlier in this thread IIRC that someone has started IOT at age 30, so it's not impossible.
Marco