I went through the conversion process about 9 years ago after having flown in the UK for 12 years. It was a nightmare paperwork wise but fairly straight forward. You have to sit Human Factors, CPL Air Law, ATPL Air Law and if you have never held an CASA issued IR before then you also need to do the IREX exam. What was frustrating was that you needed to pass CPL Air Law prior to being able to book ATPL Air Law which was an issue considering I did all 4 exams in 5 days and it was a bit of a variable as to whether I would get an ATPL air law slot. I had to do an IR exam in a Duchess to get the IR initial issued, to do the flight test I had to get a Certificate of Validation issued by CASA based on my JAR ATPL and that took me about 10 months as CASA kept requesting additional crap from the UK CAA. I know that CASA have now introduced the ATPL flight test so I don't know how that works into the process now.
I did all the theory through the Advanced Flight Theory who at the time offered a 'Foreign ATPL' conversion pack that focussed purely on the just the exams for conversion (
Overseas Convert | Advanced Flight Theory, it was initially very overwhelming when it all arrived in the UK but once you get your head around the AIP, CAO's and CAR's it was actually straight forward. Use the Bob Tait book for the IREX study. I had no issues with the exams as there are plenty of practice papers available. The flying portion I did in Perth ad Ad Astra who once again had a 10 hour IR prep course specifically for Foreign Pilots 5 hours ground trainer, 1 practice flight test in the Duchess followed by the real thing. That took me 3 days for the flying component.
As for employment, I got job offers from Jetstar and Jetconnect on the condition that I would get my OZ ATPL prior to starting, Virgin told me that they didn't accept ATPL's from a foreign conversion and if I wanted an interview with them I would have to sit ALL the ATPL exams so they could see evidence of passing the lot so I didn't bother pursuing Virgin any further. Qantas and Air NZ were years away from recruitment at the time so I didn't bother but I have had a number of mates since get jobs with both after a stint overseas. Air NZ even did the ATPL flight test for them during their conversion training.
As for flying in OZ after many years in Europe, be prepared to go back in time. It is very much GA in Jets, the rules, regulations and CASA are like they are in a time warp. The airspace is a mess, ATC will let you fly out of controlled airspace during descent into major airports and then report you for it, on the other hand it is OK to flying high performance jets into uncontrolled airports mixing with GA traffic on a CTAF frequency. Airport facilities are farcical, when I arrived there wasn't a single CAT II or III approach in the country although a few exist now, ATC into SYD and MEL is often a mess, everyone says 'but they are dealing with a lot of traffic', They need to see how it is done well oversea's. On the plus side, the airline I ended up working for is really enjoyable, the crews are good, training has been fantastic and since the change over to Part 61 licences and EBT sim training it is the most enjoyable checking environment I have encountered. (ALL PERSONAL OPINION OF COURSE)
So all in all, contact CASA and get a breakdown of what is needed, if there is anything CASA related then get that underway ASAP as the exam and flying side is quite easy to organise and get underway. The job market has been quite good although may be slowing a bit and be prepared for a lot of head scratching when you are exposed to some of the CASA rules and regs which may suit a C182 charter but don't seem to be appropriate for a Jet.
Good luck