The law changed years ago however the MOT didn't check for legalities of the headlights, just the condition of the components required to work with each light type.
The rough difference (as i understand it):
Old MOT -
Check beam height, cut-off etc.
If headlights have washer jets, ensure they work
If headlights have self-adjustment, ensure it works
New MOT -
All the above PLUS
If headlights use HID or LED, ensure the headlight assembly was designed for it.
This means, in theory, all HID kits can be failed if the MOT tester decides to. It's going to mean either swapping back to halogen once a year or a friendly chat with your tester. Our cars aren't dangerous with HIDs after all.
That said, i've just re-read it and it states....
4.1.5 Levelling devices
Where a manual headlamp levelling device (driver control) is fitted it must work. Before operating the
control, check the setting it is on and return it to the same place.
Vehicles equipped with High Intensity Discharge (HID) or LED dipped beam headlamps may be
fitted with a suspension or headlamp self-levelling system. Where such systems are fitted, they must
work; however, it is accepted that it may not be possible to readily determine the functioning of selflevelling
systems. In such cases, the benefit of the doubt must be given.
4.1.6 Cleaning devices
This inspection only applies to vehicles first used on or after 1 September 2009 equipped with
headlamp washers.
HID lamps may be identified by:
taking a few seconds to reach full intensity
having a bluish tinge to the light
having an igniter module/inverter behind the headlamp
having ‘DCR’ marked on the headlamp lens or body.
HID headlamps use high voltage and extra care should be taken when inspecting these items.