Just driving round the m25 in heavy traffic huge bits of what I assume to be the steel belt from a blown truck tyre appeared from no where getting thrown into my front end by the vehicle in adjacent lane .By some miracle upon inspection didn’t hit any of the paintwork or grill , but hit the offside front light unit , big scores in it so now needs replacing . It’s a normal ( non matrix light ) 2017 saloon . My question is has anyone replaced one of these how difficult is it to put a new unit in without affecting the alignment or will it need to be completely realigned post fitting. If anyone has the part number that would be extremely useful. Thanks in advance.