To be honest, I just don't particularly care if there is a cyclist without lights but I can see him (or her). Doesn't matter. Technical infringement of the law, and if they get caught, great. But I'm bored witless by how many times I hear people complain about the visible cylist without lights. They don't complain about, say, the cars visibly speeding on the motorway, or the cars visibly parking on the pavement.
Regarding the undertakes, yeah, that kind of sucks. Its often the problem with cycle lanes on the left of the traffic, if the traffic in the lane to the right just happens to slow right down, you're undertaking it. Oughtn't go past that van that wants to turn left there.