Woopsy. I forgot the basic cardinal rule before jumping into a dire conclusion.
Do a test first to find out for certain where the leak is coming from. If its from the windscreen as posted earlier, pour water down directly onto the windscreen making sure the water falls through the roof. Observe to your satisfaction that the cabin does not leak.
If this test is dry on the inside, then start pouring water all over the sunroof and then observe again ... bound to be one or the other.
