I was training a transferee on Brisbane Arrivals (30 to 150NM BN) one morning setting up an orderly sequence for Approach. One pilot advises he has miscalculated his top of descent and needs 10 extra track miles - we decide (with the FLOW) to vector him out and speed up and track shorten the jet behind - just swap them around. When give the heading the pilot starts up - are we being put back in the sequence - yes. We don't want to be put back, we just want a few extra miles etc etc. After a short time of similar ****, our instruction was "The ATC instruction is, turn right heading ..." Pilot promptly read back the heading and turned right - he understood he had to comply with the ATC instruction, unless he had an operational reason for not doing so.