It will fail the next MOT so sorry no fixes allowed. Does the lens come off? Are there metal clips round the headlight or is it 'glued' on? You can change lenses on german cars so worth looking.i've had a stone hit the headlight on my synergie which has left a pin sized hole in the glass. what's the best way to fix it so water doesn't get in without having to fork out for a new headlight????
solvents release gases which will mist up the inside of your light, id suggest usin clear silocone or something similar..... or even try a windscreen repair kit, available on ebay?.....If it is small, I would think 2 part araldite would do it , surely a tester wouldnt notice it?