One problem fixed!
While fitting a CTEK charger quick disconnect to the battery a while ago (so I didn't have to remove the spare wheel and suspension pump every time) I had to cut away a little bit of the red plastic covering the positive terminal. In doing so I accidentally cut through one of the BST signal wires!
I'm clumsy!
Soldered, heat-shrinked, code cleared.
Now, the driver side headlight not initialising and aiming at the floor I'm stumped on. It can't be the level sensor as that would make them both aim down right? Can the vertical aim motor be removed without taking the headlight apart?