I bought the boxed version from Play.com for £18, that's about £5 cheaper than it was on Steam.
So I waited for a fortnight for it to show, and when it does it will not install from the DVD, I ended up putting my serial key into Steam and downloading it anyway.
Was a bit miffed that I'd actually waited the two weeks only to have to download it from Steam anyway. But atleast it was cheaper, so it's not all bad.