I am under the impression that the electrical current of an HID is claimed to be lower than a halogen bulb so it should be ok, although of course most of these hid kits are chinese copy technology. I have a pair on my lotus and they worked fine, but just on the main beams. It is conceivable that if your mot man notices them and is a miserable one he could fail it because the bulbs are probably not E marked, and because HID are so bright they are only ever used (on new cars when built) in conjunction with load levelling to make sure you dont dazzle people when the boot is full of stuff.
That is why on the lotus (which has a twin headlight setup) i used normal xenons for the outer units (dipped plus main) and HID on the inners, because I think if we get into an argument come MOT i can disconnet the inners and I still have an e-marked dipped and main. Having said all that, its been irelevant becauser the car hasnt been to an mot since i did all this.
I have also been thinking about another idea for lights. Nowadays you can get some dinky little units being sold for kitcars. I am not sure if these are the same things, but i also noticed at a chinese bike show i went to that there are motorcycle headlights which are really small too. So you could make up a blanking panel in the old headlamp hole and fit these:
http://www.cbsonline.co.uk/product/4_Inch_Replacement_Headlamp_Lens_Unit_HL4LENSI know i've gone a bit tangential on this one, sorry............
