I've recently purchased a new car from a main dealer and paid for dealer-fit front and rear parking sensors. A week after purchase, it comes to light that non-manufacturer approved sensors have been fitted - even though I had specified only approved parts to be used. As mentioned in several places in the handbook, this will affect the warranty if the sensors cause failure in other parts of the car's electrical system. The dealer is adamant there is no problem and no issue. On appeal to manufacturer for help, they've recorded that the car has been fitted with non-approved sensors and they have stated the warranty position. Any ideas where I can go to for a resolution as other dealers may well refuse warranty work because there's a black mark on the vehicle.