Pretty easy to do, you'll need to strip the grey off, looks like anodising so you'll need Drain unblocker from B&Q, once the grey stuff is off get into them with progressively finer grades of wet and dry sandpaper (used wet), depending on how bad the heel rub scratches are start with maybe 600 grit, then 800 then 1200, then a Brillo soap pad then Autosol metal polish.