I think it'll have to be a Renault dealer or an independent garage which specialises in Renault, as the new key will have to be programmed to the car using the appropriate diagnostic equipment.
Register with
http://www.renaultforums.co.uk/
and ask there. Remember to state make, model and year of car, and they'll probably want to know if your key is lost or broken it as it may be repairable.
arch, June 2009