Personally I would go for the renault specialist. If you want the water pump doing it shouldnt be much extra, as once they have it all apart to change the belt it doesn't take much more time to do the pump as well. With the pump included it should still work out cheaper than either of the main dealers.
The pump might not necessarily be required, but they might be suggesting you replace it based on the logic that the belt won't need doing again until around 120k miles by which time the pump may well be shot, and doing the pump on its own will probably be as expensive as the cam belt change.