I agree it is a common occurance all over OZ and it stinks IMHO.
What you do in a situation like that is reply to the RPT aircraft with something along the lines of " J*... inbound to Ballina there a number of VFR aircraft in the area and unless you wish to wear one please state from what quadrant you are tracking from and ETA" or words to that effect. Amazing how they get interested if they think they may hit something.