I've successfully polished scratches out of mobile phone plastic screens and cleaned otherwise immovable marks from the windscreen using Peek and Solvol Autosol metal polishes. Use a clean soft cotton cloth NOT paper (which scratches even glass).
2012 Subaru Forester - capable but no magic carpet
2011 Grand C4 Picasso VTR+ 1.6HDi - not missed!
1995 Xantia Estate SX 1.9TD in Vert Vega "The Green Lady" - sadly missed
1998 Xantia 2.1 VXD Estate in Mauritius Blue - R.I.P. (terminal tin-worm)