Hi there,
Long story short, don't bother trying to go through official channels to get them certified. No-one is interested in helping!
What I did was find a tester who understood that the whole UK vs Aus standards for identical tanks is bs and was prepared to hydro them.
One they have been tested in Aus they are in the system, so to speak, and you won't face any more problems on your yearly(!) visit to the testing station.
Unless you strike it lucky, try and find a tester who is independent of dive shops. If you try to talk to anyone in PADI world you will either get a blank look or a flat no.
Where are you? I am in Sydney and might be able to point you in the right direction if my guy is still in the business.