Continued searching on Trove has yielded a couple more caravans of different styles.
From a pictorial page in The Courier-Mail, 23-12-1938 a photo of a van being checked by police for registration. No origin is mentioned, but it is a similar style to other vans of the period with angular windows and no wheel arch.
A much more stylish van appears in this posed photo in the Chronicle (Adelaide) 9-2-1939 generally promoting the joy of caravanning. No rear window or hatch is evident on this van, and it would appear with the awning mounted on the driver's side that the door might be on that side too.
From The Farmer and Settler (NSW) 2-3-1939, a home built caravan, again with the door on the driver's side and in a fairly basic style. I'm always intrigued by the paint patterns used on these early vans. On some factory vans it seems it was almost a trade mark, which made the van readily identifiable.
George