That's about the drive to Culbin from Sheffield. When you get there you get a much bigger area of dunes.
Surely there must be bigger/better dune areas in Oz?
Pittwater dunes in Tassie - maybe 15 hours driving and an overnight ferry.
A heap of dunes that are protected near the cities in the SE of the big island.
Simpson Desert had a lot of dunes, would have been very challenging, but about 5 days driving.
Best option is probably to find some that some farmer owns and doesn't want.
Some great forested dunes near Newcastle, but they are waiting for a fire to go through to make them runnable.