Strictly speaking, and if you want to comply with the letter of the law, you will need headlamp washers AND automatic self-levelling of the headlamps to ensure that you don't attract any unwanted attention.
I have fitted these to my A2 and it passed the MOT with ease earlier this month. However, many, many people choose to fit these kits without adding the 2 other bits and they get away with it.
Whether you choose to or not is up to you, but what is undisputable is the added performance over halogen bulbs, no matter what type: +50%, +80%, Silvervision etc, they are all completely beaten by genuine xenons.
I now have genuine RS4 bi-xenons fitted to Tank, with projectors and a modded beam shield to give an ultra-sharp cut-off and a nice blue wedge, as opposed to a re-based kit though.
Cheers,
Mike