I live in the US, and I know that you could only get the audi RS4 Avant pre-order bonus if you pre-ordered the game from some electronics store in england. That is one of my favorite cars in forza, and I don’t know if UK codes work in the US, but if they do and somebody has a code they would be willing to sell to me, I would be very gracious.
Selling codes constitutes commercializing accounts, which is against the Xbox Live Terms of Use, so we can’t allow it here.