Cheap rent-a-van in Canberra?

Thanks for the tips

The hire car companies have trucks that are usually heavily discounted during the week because obviously everyone wants to use them on the weekend.
Pick them up at their city locations rather than the airport and you save the ‘airport tax’ that Terry Snow et al collect as part of the rental.

If you are looking at using one of the commercial stroage facilities around town, check to see if they have a suitable vehicle available. Some of them offer such a vehicle for free.