Carp3Di3m

Hi all, just 2 days ago I went to kwick fit and let them full service and MOT my C3. Last weekend I saw that my left front light isn't working.I told the mechanic to fix that, what he did. Then I got the car back (it was raining on that day) and a day later I recognized that in that this light is no full with condensed water!. I called them up and they all (3 mechanics) said that it was like that before but just before I gave the car to them I checked that light and there was no water! The light is working but the water is over half the light now. So what shall I do now? Shall I look for legal advise? I called the customer service and they didn't care about this problem.