UKPassats

I have been looking at HID kits for my ssat And was wondering how road legal these kits are, some state for show or off road use only, what would make them fail an MOT? has anyone on here been failed on an mot for having these kits?
I figured the bulbs, as long as the colour was ok couldn't fail because the lenses are projector types on a Passat
what do you lot think??