Is a Body Kit or Wide Arches Legal in the UK?

Why?

The Construction and Use Regulations require that a vehicle and its parts are not likely to cause danger. For bodywork that means no sharp or dangerously protruding edges that could injure a pedestrian, and everything fixed on securely. A well-finished kit meets that easily; cheap, brittle or badly bonded parts do not.

The rule owners most often miss is wheel coverage. The bodywork or arches must cover the full tread width of the tyre when viewed from above. This is why wide arches exist: they let you run a wider, more aggressive wheel-and-tyre setup while keeping it legally covered. Poke tyre outside the arch line and it is an offence.

Finally, nothing added may hide the lights, indicators or number plate, or block the driver's view. Kits that relocate or partly cover lamps and plates are where a cosmetic change turns into an MOT and legality problem.