309 sunroof leak

[pazz]

My 1993 309 has the manual sliding sunroof with vacuum operated seal. Rainwater is getting in somewhere in the area of the sunroof. The main seal looks fine and I've already replaced the sealing washers on the handle. The two drain holes at the front of the frame look clear. Theres also one at the back corner of the frame on the passenger side. I've shone a torch down the hole and I'm not sure but it looks like the pipe has come adrift just below the drain hole. How do I get access to it - remove the headlining or take the sunroof frame off from the outside? The Haynes manual is useless - it doesn't even mention the sunroof, or the headlining.