My Ka is nearly six years old, with about 24,000 miles on the clock. It has badly rusted at the bottom of the driver's door, on the inside, above the sill. The sill also has rust spots both inside and under the car. My local Ford dealer claims that Ford will not cover the rust under the anti-perforation warranty, because it has been caused by grit in the rubber door seal or seat belt damage. The warranty expires in September. Further inspection has revealed the problem to be in its early stages on the passenger's door sill.

I have been quoted £300 to rectify the problem on the driver's side (the fitting of a plate, not a new door) and £200 for the passenger side. I intend to keep the car until it is no longer financially viable to repair it. Is there any way to force Ford to honour the anti-perforation warranty, or least contribute towards the repair of what appears to be a common problem in Ka cars?