Depending on if you have 'angel eyes' fitted, aswel as washer jets for your headlights. If you read the small print in your box/instructions, all HID should be used in conjunction with self levelling headlights, projector lamps, washer system for the headlight itself. My mates dad owns a garage, and I have seen many cars fail due to having HID's fitted in normal headlamps.
I'm not saying don't run them, because I have used 6000k HID's before on my previous car.
It's also a very vague subject with VOSA.
Your more than welcome to google it, and I'm pretty sure VOSA state if the headlights give of a scattered beam pattern, your car will fail an MOT, depending on MOT testers discretion.