Some pics of the Morris CS8 water tank.
Begs the question: What became of the rest of the truck ?
And: How did this vehicle get to Australia? Maybe "refugee cargo"
This tank did not come off one of the Bedford MWC trucks that are listed in the AWM 126 books, which are incorrectly listed as 30 cwt OX models.
The water filter material/powder they refer to in the film is known as kieselguhr
https://en.wikipedia.org/wiki/Diatomaceous_earth