Ignoring for a moment the Flasher Unit itself, focusing only on the 49a/L Load pin which sends the flashing signal to the various lights, where does the lightgreen/midblue wire from this pin travel after this?

Obvious the flasher unit flashes but it doesnt give an directional information, just the on/off flashing, so how does the indicator stick or whatever is at the destination of the green/blue wire determine left/right flashing?

What is switched on or de-earthed by the stick or relay to determine this choice.?

 

It goes to the indicator stalk and also the emergency flasher switch.

Indicator switch sends the signal to the left or right, just a simple switch that provides continuity to one side of the car or another. Nothing else is turned on except bulbs.

Think of the indicator stalk as a simple changeover switch. At rest it doesnt make contact with either side. You operate for a right turn the contact makes the cct to that side and the flasher does its thing