This is probably a dim question (particulary if you still have halogen lights) - why practically are LEDs/HIDs a bad thing, ie a MOT fail? I would have thought they would actually be.a safety feature - my MG Midget and 4/4 both of late 1960 era light up the road in a much less satisfactory way than my modern SEAT Leon with LED headlamps.
Dave it is because the lens needs to be different to manage the light spread, the self levelling is to prevent the extreme dazzle that can be caused.
