Now that is what I call CLEVER!
Remember folks, you can't print white on an ordinary printer, only something like an Alps. You need to buy white decal paper for laser or inkjet. In the latter case you need to spray with clear lacquer to seal the ink or it will run when you soak it. Decal paper is available from www.craftycomputerpaper.co.uk. Great service.
Oh, and another easier way to produce licence plates is to download a plate through Google images and resize. You could find a photo of a car with a suitable plate and crop the image down, or even take it yourself, maybe even the plate on your own car. This way you also get the light and shadows right.