I suspect the best you can do is get confirmation in writing rather than a replacement.
As said above, it's been a while since the certificates have been PPP ones. Pro R took over with later model Impreza/WRX STis.
You never know your luck though, IM may be able to provide a replacement. You could always try Prodrive direct too.
It's a shame Prodrive and Subaru UK aren't bed fellows anymore. At least Subaru of America like them...
http://www.autocar.co.uk/car-news/mo...wrx-sti-livery