Hi Jay,
Agree with Grey DJ here - this should be fine for DVLA. But as you've posted here as well as emailed, I'll answer here without giving your VIN away. Your Cavalier in Oz was built in Antwerp 1 and is a 1985 B reg mid spec cavalier. If DVLA won't suck it up I am happy to provide a dating letter to this effect based on the VIN.
Cheers.
Andy