Just an update. I removed the cover around the steering column, the panel with the small shelf by your right knee and the instrument binnicle. No sign of a flasher unit. However, what's strange is the ticking sound of the indicator comes from inside the instrument binnicle. Testing the indicator without the instruments plugged in..... The indicators still work, but without the ticking sound (bar the rear left which is the broken one). I decided to test the tail light unit, so I swapped the left and right tail light around. The right light worked perfectly when it was plugged into the left side. The left light however didn't work when plugged into the right side. So it's definitely the rear left tail light unit, and not any loose wiring or relay. Time to order one