for legal xenon headlights you need;
1) headlight washers
2) auto leveling (sensors in suspension tell the headlights to auto - angle themselves. )
3) projector headlights for the legal pattern
i have aftermarket HID kit with projector headlights, so 1 of 3 in the checklist. i have successfully passed 3 M.O.T's with them on, and as above if you fail, just fit standard bulbs for the re-test.