Hi Airmaster,
I coverted my South African PPL to Australian around 18 months ago and have subsequently help a mate and my Dad with the same.
My first comment would be that an Australian PPL is perpetual - it doen't expire. I would suggest you do the PPL validation now so that you have it if you ever need to fly bigger stuff later.
Secondly, a PPL does not entitle you to fly RA-AUS aircraft. Ultimately therefore, you need to do the license based on what you plan to fly.
I also found that what the regs require and what the flight schools want are not always the same thing.
1. The process to validate your PPL starts with an application for an Aviation Reference number (ARN). This is the last thing you'll get for free.
2. You then submit the application form to CASA with certified copies of your logbook. They will contact Canadian Authorities to get a confirmation letter.
3. At the same time you'll need to apply for an ASIC.
4. Once they have received this, they will send you a complete license print that requires one signature from an instructor - and this is where waters get murky.
5. The instructor's signature will be that you have passed a Bi-annual flight review. That's all. This said, he also needs to confirm that you are familiar with Australian airspace classes and the local area. Our instructor required a separate flight to each of the 3 surrounding large controlled airports, as well as a transition through nearby militrary airspace. All in, it was 3 or 4 flights and he signed the license. You are then legally allowed to fly VH-registered aircraft.
6. The concersion to RA-AUS from PPL requires 5 hours in a RA-AUS aircraft, and then a flight test.