The MY date is the model year date and is often one ahead of the date it was manufactured.

MY = Model Year

 

As above model years normal fall with reg changes but this was not always the case with Rovers and MG's.

 

MG Rover used to change around March time. So the first 5D car was built early 2004.
This last decade has caused a lot of confusion about that. Build year on the VIN has nothing to do with your reg number.
The latest MG TF has reverted to VIN AD for 2010.

 

Thank god for that I was thinking it was nicked :O Cheers guys!