time for a bit of a clarification...
International 0800 dialling is most definitely possible! Telecom and Telstraclear only implement the call routing and billing options that the customer wants. So for example if AA (0800 555 222), etc do not work from overseas, it is simply that the companies involved have not brought the international service.
If you feel this is a service that the various companies you want to call should have, I recommend you contact them directly. Here's the information you all want...
All options are covered, including inbound, outbound and billing! Also, for residential calling refer to my earlier post about Home 0800.
Hope this clarifies things for you!
ps Thanks to Jama Bob for the directions!!