Ah, in that case will need them. And for ledgal reason you will need the leveling sensors on each pass side suspension arm? Heaven forbid anyone should flout the law on that one.
Insurance could be an issue if you have a prang, should they find any irregularitys, they will jump at the chance not to say out, if not notified or up to spec. But you dont need of to tell you that....
Grey area - when your car goes for an MOT and has a good, MOT standard beam pattern, it HAS to pass, therefore making it road legal.
It's "suggested" by the DoT (or some other mob), that HID lights should be fitted with washers and a levelling system, but, IIRC, not actually law yet........as far as retro-fitting them goes.
This is to do with cars fitted with reflective type headlights.
However, on projective lights the dip beam on Omega is projective), this all changes as the burner (bulb) is not seen directly, merely the light reflected from it is.
So that's why the main beam on Omega is halogen powered, as that is reflective.
This was all put up on
www.clubcalibra.com a while back, and in conclusion - my old Calibra would have been "more legal" with retro-fit HIDs, whereas my Carlton would be "less legal" with them.
They work fine as dip, main and spotlamps on my Carlton, I have to say.

As far as insurance, I think that if the car passes an MOT with them, then all should be well, as the car is roadworthy in the opinion of a representative of our wonderful government - i.e. an MOT tester.
Proving they were fitted at the time of the test is another matter, though. :-/