Battle vs Chess, Chicken Shoot 1 & 2, Earth 2160, Enclave: Shadows of Twilight, Gorky 17, Heli Heroes, Jack Orlando: Directors Cut, Knights & Merchants, Septerra Core, Two Worlds [Goatee Edition], World War 2: Panzer Claws 1 & 2, World War 3: Black Gold, X-Blades, PC – £9.36
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.
It appears that none of the games require (or allow) Steam activation.
Are any of them good, other than Battle Vs. Chess (aka Check vs Mate)?