We have an elderly Focus that has suffered the common problem of "clouding" of the surface of the polycarbonate headlamp lenses. This can, I am told, lead to MOT failure. Whilst there are (relatively expensive) products available which claim to remove the clouding, I have found that polishing the lens with T-Cut removes the clouding, with no visible damage to the lens, restoring the headlamp performance. Hope it's of interest.