Old thread. But I discovered a serious rain leak that enters in behind the rubber Where the windscreen meets the roof gutter (top of pillar.) and runs into the car behind the airbag covers just inside the door. Strip away the trim and ™ a hose over it. It is likely to do the same at the back too!
alternatively it may occur at the bottom of the pillar where the cowling lifts from the windscreen. Entering elsewhere