huh, i did not know that World Pay had an email template system like that, it looks like that would allow you to change some basic information in the email, but it wont allow for showing the product specific info in the email since that information is never sent to world pay.
that page also talks about payment notifications which is a post made to a page on your site:
payment_response.html
you could use that to trigger a universal email receipt to be sent that included the cart information and the order number.