Maybe Berberis darwinii - Nepal barberry Think that was the same species which was about 3 metres high and near the carpark. Removed about 2 years ago and replaced with a grove of Allocasuarina littoralis
When I was doing some research I came across Berberis glaucocarpa which seems like a better fit - not too sure though cause there doesn't appear to be any records of it naturalised in Aus.