These threads may help you depending on the marring type:
For bmw specific issues that may/may not apply to the 1:
http://www.autogeekonline.net/forum/...bber-trim.html
For rubber weathering in general:
http://www.ehow.com/how_5925478_remo...ck-window.html
For a dressing, you can try a trim restorer such as Black Wow:
http://www.autogeek.net/black-wow-trim-restorer.html
As far as a protectant, I would suggest 303 Aerospace
http://www.autogeek.net/303aerprot.html