Aust Army Austin Champs had chassis number in the 15XXX and 16XXX range.
Thanks to Gus Gower's good work on Champs, some details of your Champ are available:
Chassis number WN1-09281 was British Army Champ, registered number 92BE81. Those built in 1955 range approximately from chassis 8277 to 11732, so yours in an early 1955 production FFW version. That fits with the change from CT to GS designation. The 'CT' designation means Combat Truck. This was altered to GS (General Service) in mid-1955.
The British Army vehicle designation is the FV1801A/1 for the Austin Champ Fitted for Wireless (FFW). (The cargo/personnel Champ was the FV1801A).
Original engine number was 61010. This is a Rolls Royce B-40 No.1 Mk5A model.
It was disposed of from British Army base Ruddington, near Nottingham,UK, in mid-1966.
Unit sign: Red over Blue horizontally divided is the Arm of Service colours for an artillery unit. 72 is the unit number code for a particular unit within a formation, but I do not have a listing for the British Army. To work out which particular unit the vehicle was assigned to you would also need to find the Formation sign.
303Gunner is right: looks like you have one of the imported Champs.
Have you thought of joining the Austin Champ Owners Club (ACOC)? Very big pool of Champ knowledge there.
http://www.austinchampownersclub.com/Mike