Ok then why are so many conversion kits sold or am being naive. I’m guessing then that it would fail an mot if fitted ?
MOT Rules:
MOT Manual HeadlightsInoperative levelling system - MAJOR
Inoperative light cleaning system - MAJOR
and
Existing halogen headlamp units should not be converted to be used with HID bulbs. If such a conversion has been done, you must fail the headlamp.
However if your MOT doesn't spot your HID conversion, you may get away with it.