Maybe the idiot driving rules, but I don't think a single headlamp comes into things Martin.
I suppose it does have a car type body, that is a body tub with side by side seating?
Talk about lack of joined uo thinking! In the meantime, I think a reasonab le bib would find it hard to pin an offence on a driver missing the front plate, especially if had 'just been knocked off by a careless parker, officer'.