On my van, there are only small white cover caps on each end of the number plate holder, and each end of the mudguard. Those small covers you show look good, but now I have ordered pan head stainless screws, I may need to order some countersunk stainless screws to use with them (looking at the picture)! Parts now ordered...

Here are the pictures I promised of the painted parts:
Eriba-parts-1.jpg - Bild entfernt (keine Rechte)Eriba-parts-2.jpg - Bild entfernt (keine Rechte)
I can't recommend the paint shop enough. Called Aurora Refinishing, it is run by Richie and based in Buckley, North Wales. He is a true professional! As well as my Eriba parts, I have seen his work on classic (and non classic!) cars and have always been impressed by the finish. Find them here: https://www.aurorapaint.shop/