It really depends on where you have it fitted. I should Imagine Renault will charge a fortune for the part and fitting, so it might be worth trying a few local independant garages.
Newish, and at a dealer I reckon you'd be looking at �400 plus. For my VW the part was about �200 and the fitting a little more. Sorry I can't be more specific, but the dealer should give you a cost. If you are worried he's overcharging you, try another one. Also, look for a local specialist as Jay70 suggests.
Your looking around the �200 mark because what really is an easy job requires the removal of the timing belt this is what pushes the price ( labour cost ) it is worth considering getting the timing belt changed at the same time as the pump as this has to be removed anyway