I also have an FAA IR which I completed in November 2003.
I will be doing the JAR IR conversion in March which means that it will still be valid and current.
Even if it wasn't current or valid I would only need to do the 6 approaches, intercept and track courses and perform holding procedures. This would all occur on the conversion course anyway and thus revalidate the license for the issue of the JAR IR.
That's my understanding of it anyway.
Don't know about the Aussi rules though.
FIS