hi anyone know the size of the plastic scrivets that hold the sill trims on, i will replce them with new ones,      and how to get them out mine just turn around but won't come out.      car passed mot but the guy reckons the sills are corroded,   but he can't see them properly for the trims,   so it's an advisory,       i am going to take the trims off and have a look, any advice.        thanks, dek.