Here's a good analysis, by the very sound Fraser Nelson in The Spectator, of just what David Cameron has achieved with regard to the Libya situation.
It also debunks the myth that France's president Sarkozy was the primary driver: he was using ( and manipulating) this for his own political ends. The second and third paragraphs in the linked article show this quite clearly.
It has been a remarkably statesmanlike job that Cameron has done, impressive for one so new to actual government. He still has his critics (some of them in the comments to that article) and the media management of this government could certainly do with some improvements, but overall this is the kind of Prime Minister who engenders confidence, not only that of the country's own people but in the international scenario as well.
He is almost infinitely better than Gordon Brown, for a start!