somewhere around Dubbo, and from then on Airservices have no idea where I am, same as before? Is it just that it's not working yet or is coverage exactly the same as it was (is) under the old radar system?
ADS-B has been working around the country and used operationally by ATC for some years.
Not sure what you mean when you say "Airservices have no idea where I am".
On the assumption your ADS-B unit is working correctly (you've verified that at some stage with ATC, right?) then if you are within the coverage areas of sites you should be being seen.
ADS-B coverage | Airservices
If there is some problem with your ADS-B setup or planning, you might review this:
http://www.airservicesaustralia.com/...ckage_V4.0.pdf