Just Cause 2, Kane and Lynch 2: Dog Days, Lara Croft and the Guardian of Light, Supreme Commander 2, Tomb Raider: Underworld, PC – £4.79
All except Tomb Raider: Underworld register on Steam.
To purchase digital games from Amazon US, use your UK Amazon account, and add a US billing address to your account. This address needs to be a valid US address, but nothing will be sent there, and you can access all your games through their website. Some card issuers may charge a fee.
Underworld registered on steam fine for me.