mr blue i know ure problem, whats happened last week its been very cold, so your rear washer pipe has frozen up, and u have tried to wash ure rear window, witht he force of the water the hose has coem off the clip and been sprayign it everywhere inside the boot thing, so the water has made the lock get wet and corroded the switch aways, so ure alrm is goign off randomly, anyway u only aneed a new lock its about 24 quid from dealers, piece of pi$$ to do , cheers