Hi Graham and welcome to the forum.
You can only do an IVA in the UK if you have a permanent UK base - ie residential address - or have lived in the UK for the majority of the last six months. If you do not fit this criteria, you will need to look to Australian legislation. I have attached a web-site which you might find of interest.
http://www.itsa.gov.au/
A Debt Agreement is the nearest thing to an IVA in Australia, and can include UK based debts.
Good luck and let us know the outcome in due course.
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
For further details contact me at
http://www.melaniegiles.com and view my IVA blog at:
http://melaniegiles.blogs.iva.co.uk