Renault Megane Diesel Problems

I understand your frustration; I also agree that diesel buyers should be made aware of the possible consequences resulting from the way they will use the car. Blocking of the DPF because of being used on short, low speed trips is quite common across most brands, so it could be argued that you should have done you homework and known that. As to whether you have good grounds for a refund I can’t say, but I suspect you could request a refund, or part refund, as a gesture of good will from Renault.