Tee is correct about cars with xenons legally needing both self-levelling headlamps or suspension along with headlamp washers, the latter being down to the fact that xenon light scatters vey easily when dirt is present on the headlight glass, as he mentioned. However, as long as the light emitted is not blue and blatantly not standard and the beam pattern is good, which it will be with projector headlamps such as those on a Supra, you will have no problems with the police or come MoT time. I have never had problems with either and I have never heard of anyone getting in trouble for having aftermarket xenons. It's only when people start fitting xenons in cars with reflector or fresnel optic based headlights, which just don't go together at all, or fit stupid blue bulbs that there's a good chance of getting pulled over.