the vehicle is licensed, so somewhere in its history something has gone astray?
Not really - the ID plate on the firewall is not used as part of the formal identification of the vehicle. The various authorities record only the engine and chassis numbers. The ID plate (whilst it does uniquely identify the vehicle in a sense) was used to record mainly for GM-H's purposes in recording the colours and trims used on the car for any subsequent service requirements.
FantaC, your van was originally Adobe Beige with a Mesa Tan interior, and factory fitted with a glazed tailgate. Check out the
ID Plate Decoder, which will give you all the details.
cheers
RET