As a recently retired tester who asked dvsa about the led bulbs fitted into a headlamp designed for a halogen lamp and how they stated hid is an immediate fail, they also said an led light source is not compatible with a halogen lamp unit so is also a fail.
ive tested a few with led headlight bulbs and the pattern is generally awful and incorrect anyway.
they were marginally better with headlamps which had the pattern in the glass rather than reflector.
retro fitted led bulbs or light units in indicators, brakes, sidelights are all ok for mot.