I always thought they used a beam defractor to align the lights on a car and to MOT test them.
Also although right hand drives lights are better because they actually light up the right side of the road you can get a left hand beam pattern light through the MOT by covering up the section of the light that defracts the beam to the right and that is perfectly legal.
I personally like the angel eye lights but the only ones that look any good are the FK automotive ones and they are about 179 bar for the pair.
stupid money.