Hi mate,
Ive not been on here in a while but just popped on and saw your post. Funnily enough I have been playing the leaking sunroof game too but I have eventually won and have a nice dry car again
From your sig pic it looks like you have a 3 door (a3 or s3) which should mean yours should work the same as mine as I have an S3.
If your finding water around the rear 1/4 windows and also near where the rear seatbelts are mounted (in those flappy bits in the boot) then your is probably leaking where mine was too. I only noticed as my car was constantly steaming up when parked up and then the airbag light popped up on the dash. Quick scan told me it was the rear seatbelt tensioner and on closer inspection it was pretty wet which was why I had the light on the dash.
First off I thought it might be the rear windows not sealing up properly but I tested them with a pressure washer and they were ok.
It was whilst doing this that I noticed that the roof lining above the rear windows was really wet. So it was time to investigate more, So I removed the trim with the rear interior lights in and then the trim in the corners (both just pull out on clips but its not easy and I was sure I was gonna break them) eventually I got them off intact. This allowed me to pull the roof lining down a bit above both rear windows so I could see whats what.
So know I could see there is a green hose that runs around the window and down the body behind all the trim I had removed. This hose connects to what looks like a little plastic tray hidden in the roof lining. Its just as push fit so I pulled it off and got covered in water! So knew this was my problem.
I undid the clips holding the hose in place and managed to get the open end out through the gap with the rear window open. I took the executive decision of blowing down the pipe and low and behold it was blocked solid. So I got my trusty old tyre inflater and found a suitable end that fitted in the hose. Whacked it on like 55psi and flicked the switch the air moved whatever was blocking the hose and whoosh loads of water pours out near the rear wheel. I then got a jug of hot water and poured the pot down the hose to make sure it was 100% clear. I repeated the process on the other side of the car as I didn't want to have to pull it all apart again soon and that wasn't 100% blocked but it did improve.
Re-fitted it all and got it all back together ok and have had the car drying out for a few days in the garage with a hot air blower in it. Its been outside now for a while and I can confirm I have no leaks now and the car hardly steams up at all if left.
Anyway hope this helps you resolve your issue as a damp car is no fun at all
Rob
