| I've used a Maguires product (can't remeber the exact name and it's very dark and cold outside now to have a look!) that works very well. Kind of like a 'back to black' but doesn't leave the plastic feeling horrible and sticky and really brings out the colour. I have found the rain has a big impact on it this time of year, and the marks do come back, but i'm hoping with a bit more time it will build up and really clean the plastic. Halfords should do it, I've heard the whole Maguires range is very good. Anyway hope that helps! | 
