My GTI just failed its MOT for a broken front self levelling sensor. I've investigated and all that's wrong with it is the plastic ball joint socket on the bottom end of the little metal rod has departed company and vanished somewhere. The top ball joint was stiff but soon loosened up with some WD40 and wiggling, I would heartily recommend checking yours and making sure it's nice and loose if you haven't already, it can be accessed without even taking the front wheel off by turning the steering to full lock.
Sorry the pics are a bit rubbish, it was dark and I only had my phone for a torch.
As you can see the sensor appears fine and it's only a tiny little plastic part that is missing. Does anyone know if it is possible to just get this plastic bit or the whole rod or is VW going to want me to buy a whole sensor? Any part numbers that anyone knows would be great too.