Hi ,have you got to do it in 12 hours?
we recently did the great ocean road we stopped at mount gambier for a night to see the blue lake and gardens (fantastic palce to have a look and walkabout) then drove to warrnambool looked around the coast for a couple of hours then on to apollo bay for another night lovely beach then on to melbourne.
we do have 3 kids so we had to stop, but you have got to see the twelve apostless (maylbe take a romantic helicopter ride about $100 to look at them).
Dont rush it (if you can).
the motels are really good value also
If you want any more info just ask