It was £14.99 on the argos site last week, I remember my girlfriend sending me the link.
I picked up PGR 4 at the weekend from Gamestation (2 for £40 quid deal) and I love it, I think its a huge improvement over PGR 3... I mean, they have the Sierra Cosworth 500.... No game has the Sierra Cosworth 500!!!!! Its just pure genius!
... So yeah, good game.