Hi Colin
Alan Collett can tell you about this. He is a Registered Migration Agent, lives in Melbourne, runs at least one company out there - Go Matilda - plus he is a Chartered Accountant in both jurisdictions.
It would be worth paying him a few quid to get him to give you a bit of advice, I suggest.
He can be contacted via e-mailing
alan@gomatilda.com or via the contact details on the GM website.
Also, he has an accountancy firm in Southampton (UK) called Collett & Co. You can download fact sheets from the site. I've just had a look and there is one about setting up a business in Oz. Please see this link:
Collett & Co
Cheers
Gill