I know the MOT is funny with the lights now. Can be bright to dim, if you can't adjust them, or if you have Hid's and the washers don't work, they all result in a fail. Dam the EU ;)
Other then putting after market lights on the car I never done any tints to the lights. But you just reminded me I was going to look at getting some LED side light bulb's... Cheers mate ;)