Then you should be fine, assuming it's a legit key.
I learned there are actually websites that do this. CJS Keys is a store that stocks thousands of legitimate copies of games, and simply sells the keys online for damn cheap. You can buy Battlefield 3 for $39.99. If you look at the Steam section, they have Space Marine for £17.99, Dead Island for £21.99, and Deus Ex: HR for £22.99, among others. They seem sketchy at first, but apparently they've been around for quite a while, and they get favorable reviews.
Not an advertisement, I don't work for them, but it was on the front page of Reddit today and I thought it was interesting.
And yeah, they have keys for North America.
Edit: This is what was posted on Reddit. I guess it was mostly intended to stir up hype for BF3, but you can see it's from CJS Keys:![]()
They only seem sketchy because you don't realise that people in the UK can get boxed copies of those games for those prices.
I personally can buy Space Marine right now for £17.99 from Amazon.co.uk, DE:HR for under £20 from Amazon.
UK boxed game prices are cheap.