We moved to mackay Queensland, bringing our Panasonic viera TH- 42pz850az, unfortunately it doesn't work here. We can switch it on, but it won't tune,
Have had a professional aerial man out, replaced the aerial and connectors,
Can you help

It's entirely possible, if it worked fine in New Zealand, that Australia uses a different tuner.

After some very quick research, it appears New Zealand uses Freeview, whereas Australia uses DVB-T. So the tuner is not compatible. It looks like your best option would be to get a tuner box/set-top box.'

EDIT: And not seconds later do I realize that Freeview uses DVB-T and DVB-S. *facepalm*

Does your TV not pick up any stations at all? Do other TVs work?

Also check Panasonic's website for firmware updates (sometimes this might fix issues similar to the one you are having).