Grey Plastics

can recommend highly Black Wow, pricy but lasts years, you only need a few blobs and it spreads well, lasts and beads nicely, leaves a darkened finish.

http://www.motorgeek.co.uk/black-exterior-trim-restorer-with-free-applicators-p-384.html

see my review and pics here
http://www.fordfiestast.co.uk/showflat.php?Cat=0&Number=408058&Main=407780#Post408058