'Technically' with xenon lights you need self levelling headlights, and washers to comply with constuction and use regs. All cars with oem xenon will have that, but I've never heard of anyone with projector headlights and HID's have any problems. I've had three Mot's with mine in, and it's never been mentioned. The worse that would ever happen is you would be given 14 days to remove them.
Standard wattage is 55w, stick to that in your dipped beams and you won't go wrong.