The best contract deals I found were via via nokia direct (I think it may be out-sourced to MPC). Quick a bit cheaper than 'voda' (You really must ensure you get a data package). If you add up the "total cost" of the various deals they virtually all come out to the same (for a specific duration) - no surprise.

The best one-off charge I found was via www.quidco.com/nokia which is currently offering 10% + 20% off taking the price to 360, although there's a glitch at the mo which means it seems more like 390

(UK, UKP)