It's also worth checking that while the mod is listed and won't void the policy, that the mod itself is covered in the event of a claim, as some insurers will take note & charge a premium for the modification but will only return the vehicle to factory spec.
I had the misfortune of finding this out when a truck scraped my side, as the Paintshield film I'd fitted to the front wasn't covered and I didn't want to pay another £500 to get the wing & bumper redone.