On another forum I am a member on, this same subject came up - a few members in the end wrote into various organisations to get clarification on this situation, as the legislation that I have seen only refers to manufacturers fitment - original equipment. All the answers we received said that we were ok to use retro fit kits. Since then quite a lot of members have fitted these, with numerous MOTs. No one that I know has been pulled by the police for them, or been told by an MOT tester they are not allowed them. Provided they are fitted correctly and are properly aligned, I dont personally think you will have issues with them. This is of course only my own personal opinion. Other people on this site have raised very good points as well - at the end of the day it is your car and therefore your choice as it is you that is responsible.