I agree totally with Tunnie, headlight washers do serve a real purpouse. I would not even consider only fitting the lights, in my opinion you MUST fit the correct sensors to make the light motors work and headlight washers. I think it's bordering on unsafe and careless not to fit them. They are there for good reason, and by-passing them can only lead to trouble. I think not fitting headlight washers negates the whole point of fitting HID's...you want better light output so therefore you also need the headlight washers. And the light levelling motors are to avoid dazzling oncoming drivers. I know of an instance around here, that after investigation by TVP and other agencies an accidnet was attributed to a driver who thought he culd fit Xenon's without correct self levelling, blinded a driver coming over a small bridge, and caused them to crash, causing them to suffer fairly severe injuries and right their car off.
Quick answer, if you do it...please do it properly and fit headlight washers, and correct levelling motors etc.