Digital products restrict by country

I am creating a shop for a family history society to sell books and cd’s which I can sell to certain Countries. That is easy but, I am also needing to sell membership to the UK at one price and World wide at another price. I can’t see a way to apply restrictions. For instance if I enter an Australian address in the checkout page after purchasing UK membership it will process the order and not reject it. Any ideas please. I am using WP Ecommerce.