DT
First of all, I assume that you have an Aus licence (I'll take that as a given).
To be able to attempt an IR rating ("Rating" in Aus means that you have to do a flight test with a CASA FOI or Authorised Testing Officer (ATO)for it to be issued). Yes, you will need to have the IREX exam pass under your belt PLUS the minimum aeronautical training as well. Basically this means 40 hours of instrument time. 20 of these 40 hours can be in an approved simulator/synthetic trainer.
The IR test can eiher be single engine or multi engine. Whatever way you go, the aircraft that you use for this flight test has to be IFR equipped and certified. If the wallet can handle it, skip the single engine and go for a multi-engine rating. This makes you much more employable with the EMS and offshore operators.
Where to get IR training done???? All depends on where you are going to pitch your tent when you come back. Victoria has Kestrel Aviation in Mangalore, QLD has Chopperline in Caloundra and I think there is Rotor Lift in TAS.
There would be some operators who would hire you their aircraft for the test as long as they are comfortable with the ATO conducting the test. The types of aircraft available are AS355, BK117, B412 and A109. You must be endorsed on the aircraft type to attempt the test.
Look at
http://www.casa.gov.au/download/orders/cao40/400201.pdf to get the full run down.
Hope it helps.
