Peter, I work in the "paintwork" industry - for a vehicle manufacturer. I would definitely think twice about using a "chips away" type of company!
MG Cannon - who you mentioned (are approved by us) - will do a good job for you as they will blend the paint within the rear wing and then clear coat the whole panel...this is the correct way to complete this job.
I am not blowing smoke...however, as your car is valuable - it does need doing correctly..I know you would not except anything poor mechanically...don't then when it comes to bodywork?
regards Mark
