UPDATE!
My A5 was at the dealership recently for its first oil-change. Because of personal time problems the dealer agreed to lend me a courtesy car, even though the dealership policy at this time did not allow for a collection service or loan car. They lent me a late model A4 with a factory fitted camera, what a difference, it was everything I expected mine to be, superb image and brightness.
Asked the dealer why there was such a difference in the quality image to my A5?
He reported that the image on my A5 was different to the factory fitted camera and nothing could be done to tweak my A5 camera to improve the image, and that the kit supplied from Audi was not identical to the factory fitted one.
At this time I am still not sure why Audi can't fit an original camera, and at £650 why not?