Hi OllyH ... I have a PS Cooper with black roof and guess which is the hardest part of the car to keep looking nice? You guessed it .... the black roof!!!
I am really careful rinsing before washing always worrying about grit etc but still had swirls and light stratches which I could see. Probably no-one else could, but I could. Anyway invested in a bottle of (hang on just got to pop out to the garage, back in a second
) .... back now .... Auto Glym Ultra Deep Shine. It says ultimate polish for modern paints and dark colours and I was really pleased with the result on the first polish. It brought back the black mirror-like finish.
It is not cheap at £11.99 for 500 ml at Halfords but I think the bottle will last a long time but hey when you have spent so much on your Mini I reckon it is worth it. If you try it, please do let me know how you get on.