Well I have finally found out a little more about the Q4. It had the Army Registration Number 34 BP 91, which is chassis 38A5391 'Truck, Cargo, GS, 3 ton, 4X4, Commer Q4'
It entered service on 20 June 1955 on receipt TWN/252/61 - TWN indicating Vehicle Depot 75 Turweston.
It was 'struck off' on 2 September 1955, along with two others - 34 BP 90 and 34 BP 94. The reason for the early disposal is not known but it is likely all three vehicles made their way to Australia shortly after.
So much for the first three months of its life, now to find our what happened to it during the next 30 years !! (does anyone know where in Australia these records might be available??)
Geoff