H1 to H4 bulbs

[Fazerider]

Wookie, that's very interesting.
I had been under the impression that HIDs were supposed to have all sorts of precautions to prevent dazzle, but all I could find when I searched Construction and Use regulations and the MOT guidelines is that self-levelling and lens cleaning equipment must be functional if present… nothing banning the retrofitting of HIDs to existing housings. Where should I have looked?