Odear we feel sorry for you, we have all been there.
If they have sheared of flush then drill a hole (the correct size for the extractor) and uses an 'Easy Out' bolt extractor tool, you will find them on the web even Halfords may have them they come in different sizes (I'm sorry if you know all this) it has a course left hand thread and will unscrew the remainder of the bolt.
The bolts being out before will make it a lot easier and if they were put back with a dab of copper grease on the thread even better.