Thanks for your feedback.
Especially White Cliffs sounds like a place I should strongly consider, with also the museums very interresting.
Though you can do this in a few days, my aim is to see as much as possible during the holiday. General idea was to have an trip of ~30 flying hours in a C172 with Sydney, Whitsundays and 12 Apostels as corners and then to see as much as possible in between. (Those were recommended to me by a friend who lived in Australia for 6 month)
Florian