Buy the game at tesco(or simular local supermarket depending where you are)keep the till recipt,Go home load the game to your pc,Then take the game back to the supermarket,Tell em you cannot get the game to load,They replace the one you have with new copy.So ya get two cd keys for the price of one.
well that ain't a 100% chance it works id say but the key online it cheaper and u wont scam a supermarket,
also if u suck at lieing dont even try it u will fail and get busted,
there is a chance they ask for a verifycation from steam that the key ain't working,
so i recomand to buy the key online cheap