Yes, it's a real can of worms this one, I too have been trying to fix mine all year. If you search the forum you will find lots of other threads relating to headlights, apparently the places to look are:
1) Check the front and rear level sensors. Located in both left hand side wheel arches there's a link rod connected to the sensors, check nothing is broken/seized up there.
2) Check the motors in the lights are working, replace if required.
3) Use VAG COM to check signals from sensors.
I've been through all the above so far. When I first switch on the lights they're OK but after a couple of miles the driver's side points at the floor, a few more miles they both do. I have replaced both front and rear level sensors with no success. As the lights start OK and then move low the motors are obviously both working so I have not changed them yet. According to Ross Tech the signal from my front sensor is below range but if I adjust the linkage to make it even further below range the level improves for a time.
Oh, and it's been to Audi a couple of times too, they say there's nothing wrong with it?
Of course you can always do what I have, assuming you can get the lights to the correct level when first switched on, do that and then disconnect the motors. At least you'll be able to see at night.
