WorldPay is a part of The Royal Bank of Scotland Group, the 5th biggest banking group in the World, whose payment solutions are trusted by thousands of businesses, big and small.
Reference
Pricing - http://www.worldpay.com/about_us/index.php?page=pricing
Security - http://www.worldpay.com/about_us/index.php?page=security
Products and Services - http://www.worldpay.com/about_us/index.php?page=services
Acceptable Credit Cards - https://support.worldpay.com/products_services/services/cards.html
