Well, I've had pressed steel plates on my Golf Cabriolet for about 18 months now - all legal, bought from Europl8 at Ultimate Dubs.
They have a BS mark, but it's so faint grey from about 10 feet away it just disappears.
Now I'm an older driver so I guess the police see my grey hair and assume everything will be in order with my paper work - and it is.

Yeah, It's ageist I suppose - but it's one of the few perks of getting older