I've just had the same problem with my main lights, turned out the be the live to the number plate light had dislodged and was shorting on the engine lid. I'd start by checking the lives to the rear indicators then the fronts then the relay.
You have a short somewhere on the wires to the indicator lamps no magic cure, you have to trace the wiring through, and why have you a 30A fuse for the hazards?
Thanks for your reply with regards to going into 30A this is a 71 US Westy Spade No 30 on the the Hazard switch goes straight into 30A top spade on the fuse box
Fuse 8 from L to R
Do you think it could be the relay switch no obvious shorts anywhere