For the record…
Total travel duration: 8mths, 1 week
Total distance travelled: 27,741km (car) / 18,725km (caravan)
Most distance travelled in a day: 480km
Water: With research & planning, we were always able to access potable water. The quality did vary eg high calcium content, silt content, taste etc. Bought an additional, different inline filter (therefore 3 in total) in Darwin which made a worth while difference.
Gas: Refills proved more challenging and expensive the more remote we were. Cheapest-$20, Most expensive-$50 (Derby WA).
Fuel (Diesel): Most expensive-$1.97 (Nullarbor), Cheapest-$1.05 (Perth)
Accommodation: Most expensive-$65/night (Inverloch VIC, Broome WA). Average estimate including free camping- $30~32/night. Longest stay in one location: Olive Hill farm- 10wks+1 day.