Hi Chris, thanks for that detailed report. Running to get the map....
Just a point on cargo ships, they are possible if you can make the schedule work. One goes round at least every 55-60 days and we are looking at booking that one from Adelaide. Cost is about 500 euros and sailing about 6 days from Adelaide to Auckland. I am checking to see if there are other sailings too. Anyone interested in this form of travel can contact me for more details or keep an eye on this page, where we will add info as we go:
http://travellingtwo.com/resources/cargoship
You can only book the ships 6 weeks ahead of time so we won't know until we're in Australia whether we have a berth or not.