The wheel arch trim is often held on by a heavy grease packed in to stop corrosion. Removal is best achieved by warming the trim up gently with a hot air gun or hair drier. This has the effect of softening the grease and also warming the trim up which has a tendency to crack in cold weather.. Ease the trim off all the way run very gently at about 1/4in at a time. Don't be tempted to pull from one end or it will crack. When sourcing new trim, if you find some please remember there are two widths of trim 20mm and 30mm. The 30mm normally found on later turbo models and convertibles. When buying double check which width you are getting. The OEM trim is now as rare as hens teeth but if you strike lucky on Ebay you may sometimes find some used ones. It is NLA new. There are metal replacements available on line which I personally don't favour and you have to stick them on with silicone.