Hi Simon,
Not sure if you have made a mistake with the Contract number, or whether there is an error in the copy of the Chilwell list, but nearest I can find is Contract no. S.2245, Cat. ref. 328, which is for a 15cwt W/T House Mk.III, WD no's Z5400641 to 5403640.
And for the GS, I can find no trace of a contract for Morris trucks with number 2280.
This has made me think, because 30 years ago, I helped restore a C4, just dug out the details and it was a Compressor truck from Contract S.1622, but chassis number started 2169 C4 ***, so these numbers may not be contract refs, hence why no trace of one and the other is one digit out. :undecided:
regards, Richard