I do think HIDs are more trouble than worth, seeing as all the rules and advice seem to be open to interpretation. Clearly, government departments are trying to make retrofitted HIDs comply with new car standards. Rightly IMHO, as too many retards out there.
But even if you can get it through MOT with a friendly tester, any number of people can pull you up due to high lights or glare from dirty lenses. And their interpretation can be different. Even if it gos no further than a show-er down the local nick, its a pain.
I was often getting pulled and having to show docs at Aylesbury nick, purely because I used to drive my GTE not far from Blackbird Leys (the place that the joyriders were caught on camera in Oxford, so everytime joyriding was mentioned in the early 90s, it was that clip).
Given that Nightbreakers etc almost match HIDs (and surpass old bulb HIDs), seems too much bother for the benefit....
...now ribs to clear halogens...