Sorry to disappoint with the Prelim classes being run on Saturday this time around!
I am totally worth the travel, but I understand the predicament!
I have heard mixed reviews about Zhang's -- apparently he is quite difficult to understand, has quite large classes (25+?), but he really knows his stuff!
Synergy Education in Stra is pretty good. They really emphasise on a fundamentals approach, easy to understand and focus on heaps of exam technique. I go to a selective school and my ranks have definitely improved heaps. I went from ~40th in chem and phys to top 10 in the school after trials . Some of my friends there are also seeing lots of improvement as well.
There is also Dr Tammy Humphrey and her Fathoming Physics specialist Physics coaching centre at 38A Langston Place, Epping (0473 - 645 857) opposite Epping Station.