I know this isn't exactly cheap, but it would seem that GAME have dropped the price on the special edition from £49.99 to £39.99, making it exactly the same price as the regular edition. You don't exactly get much more for the money, but maybe it'll be a nice box or something... Link below!
http://www.game.co.uk/PS3/Action/~r343449/Uncharted-2-Among-Thieves-Special-Edition/
http://www.game.co.uk/PS3/Action/~r343449/Uncharted-2-Among-Thieves-Special-Edition/