[russellw]

There isn't a flasher / relay for either side as the turn indicators in the Fiesta are controlled by the GEM (General Electronic Module).

The left and right have different ground points but if neither front or rear are working then that is not likely to be the cause.

I'd firstly replace (not check) all the LH globes as it's the cheapest check.
The next thing would be to check all the connectors, particularly the front ones to ensure no damage to the wiring as you shouldn't see a short with all bulbs removed.

Cheers
Russ