I would have thought the onus would be on them to prove misuse. After trying the usual channels - customer service etc. - I'd be inclined to try a small claims case.

had the car from new, less then 2 years old 15,000 miles on the clock. On the dual carriageway, clutch failed. Car towed back to main dealer who said it was not covered under the warranty and i had to pay £650 as it was considered to be "drivers misuse". Only 2 days before i had it in the dealership for its service. Surely this cannot be right.

Also consider getting one of the car mags involved - What Car? seem to get reasonable success for consumers in these matters.

As a minimum, Citroen should pay £325 as a goodwill gesture, but as others say, get the parts inspected and see why they failed.