defintaly mate, if you where to have an accident and try to claim believe me the insurance assessors would know its not standard and would invalidate your insurance leavng you to cover all the costs.
as said above some companies, such as ourselves, aren't even bothered by most modifications, especailly minor cosmetic mods.
Best bet is to just ring up and see what they say, if your insurer isn't happy or puts its price up then have a shop around with some modification specialists
hope this helps

Danny
HIC