Fantastic bargain. Lots of people buying a DS to play this game, and it retails @ £35 giving you a DS Lite for £55.
The console itself is likely to be a refurbished unit, mine is near perfect save for a minor 'light' scratch on the touch screen. However, either way, they let you look at them and select one to your standards.
Comes with a years Manufacturer's guarantee too.
Not sure how long its on, GAME usually change their deals every few weeks or so or until they run out of stock.