On my daughters NC30 only the offside tail light comes on but both come on for the brake light.

Swapping the bulbs doesn't make any difference, so is this the way it is wired and if so is there an easy mod to have both illuminated for tail and brake?

I would check the wiring perhaps a bullet connector has come lose.

yeah the little loom that comes from the bulb holders connects to a small black socket my bet is the connection there needs a good poke and clean , both lights should work as well as brake lights