I bought a SEAT Leon (2010) from a car supermarket. The car was sold with an extended three year warrant, which cost £2300. When I collected the car the car supermarket told me to service the car "like a Volkswagen Golf diesel" every 10,000 miles.

They serviced it six weeks before purchase and in the service book there is no entry for next service due mileage or date. However, I did the service at 10,000 as they said verbally which is quite normal. However, later I found that the manufacturers guidelines are 10,000 or 12 months.

The last service I did was at the correct mileage (well 500 miles under) but at 13 months. When trying to claim on the warranty the company now say they have now voided the entire warranty owing to service missed. Can they do this?