Your friend is quite a risk-taker, eh?
So far my experience is that Aussie road signs regarding No Parking, No Stopping, etc are quite clear. Unless the signpost has been damaged or something, it should clearly demarcate the zone within which there is No Stopping.
My guess is that it would not be easy to appeal. Do you have photographs of the signs at that spot, by any chance?
My suggestion is to pay the fine. A$113, though quite high, I feel is a small price to pay to put this matter behind you, rather than resort to all sorts of underhanded tactics like cancelling c/c, etc.