I know I am late to the thread but if you are still having this problem I have a simple solution that I did with my cats; wrap the seat with aluminum foil and they will not come back. There is something about aluminum foil that cats hate so they will not go on it, now my cats don't scratch my couches and don't go on the dinner table or kitchen counter.
Again I know I'm late I just want to make sure that the cats don't drive you to hurt them, they don't know any better.