Hi i had the same problem and today i had someone come out to try and fix it all he did was spray some white grease into the lock itself and it solved the problem he said that moisture can build up and it is a common problem on these cars so he advised me to spray the white grease into the lock once every winter and the problem will never return. you can get white grease in a aersol from halfords for about a fiver Regards
Sean
sean sheridan, May 2009