Best advice is to speak with a consular officer. Generally, if you were born after your father had acquired Australian (or most other) citizenship, he immediately relinquished his German citizenship in the eyes of the German government at that time. If you were born after this event, you would be SoL.

As far as prior registration goes, it generally effects (IIRC) those born to German citizens who were not born in Germany. Again, consult the German consul.

The other route is through your mother. If your mother was a British citizen at birth, she is still British unless she actually relinquished British citizenship. However, whether she can pass that on to you depends on when you were born (the British Home office has a whole page on that). Early '80s is some magic date (before that and you are SoL).