Firesysok
I would disagree that an inop nav light is a minor issue for you guys Stateside. There's a lot of GA in and around commercial airports west of the pond with lots of those pilots using see and avoid, and not all of them being transponder equipped. Couple that with an overstretched ATC, I think I would want the GA jock to know which way I was going.
As for the issue of these fines, they do indeed seem to be a bit draconian. I moonlight for an NAA and in my neck of the woods the probability of fines like this (or proportionally similar) would almost certainly be out of the question. NAAs have other tools at their disposal, not only fines!