I don't believe that it would be legal no. I think the plate is required to have the correct manufacturer for the time on it. It's also supposed to have the upper number on the plate filled in which is the type approval, but you never get that on reproduction plates anyway. It could be quite foolish to fit the wrong one though because no matter how much you might be trying to make it look like an older model, it simply isn't one. If you choose to sell it then it would cause issues. I for one would be suspicious of a car with the wrong VIN plate.
First response from Google Images when asked for 'Austin Rover Mini VIN plate':
![austin%20rover%20replacement%20VIN%20cha](http://www.vin-plate.co.uk/VIN%20PLATE%20IMAGES/austin%20rover%20replacement%20VIN%20chassis%20plate1_small.jpg)
I think it's Mini Mail that will sell you the correct plate and properly reverse stamp it with your VIN if you can provide proof that the number is yours.
Edited by Dan, 12 June 2013 - 07:40 PM.