I ended up paying in the end but because the car was sold to me with the fault and the dealer (M53 Ford no less) had said at the time that the second, different, chirp was to show it had immobilised, I complained to Ford HQ and they paid half. Still cost me 100 to fix. But it cost the dealership more because I haven't been back for services there since. I go to another Ford approved garage which has a totally different attitude.