www.play.com and search for Nerf. Cheap darts; cheap guns and best of all cheap clips! Oh clips how I love thee. The Double Your Darts packs are false economy though, you're better off spending the difference between the DYD and the standard pack on loose darts. £2.50 for 36 Streamline :)
I think prices must have gone up, they are still pretty good though.
Amazon are cheaper for the double clip pack last I looked.
EDIT: No my mistake, about same price - just noticed that Play has it listed twice, one more expensive than other
I have spent far too much time looking up Nerf stuff recently, ever since it got mentioned at Fayre. Never been interested in Nerf before but now I have a few of them sat in my room [shakes fist]
Heh you should see my loft mate :D it's a veritable armoury