The next best price available is £36.85 @ ShopTo; a saving of over £6.
If a better deal becomes available between now and release of the game it can easily be cancelled, so it's a win/win situation.
Just use code JSGA2005 to knock 20% off. If you've already used it on another game you can sign up another account.
I know one or two threads have been posted regarding this 20% off code, but none of them have mentioned the deal for Deus Ex (as far as I'm aware) - and I feel it's worth another thread to make people aware of the potential saving, and for those who may have it pre-ordered for more elsewhere.
It really is a fantastic deal; pretty much £30 for one of the most anticipated games of the year.