One thing that happens on my Nikon flashes that could be worth checking is the springy contacts that push the batteries up to make contact with the door panel get squashed down every once in a while and need to be pulled back up with a small screwdriver, otherwise the flash appears dead. Don’t know anything about Olympus flashes but is it fully dead-as-a-doornail or does it power up and not flash?
I have a Nikon SB 800 which has also died. It’s powering up but none of the normal functions are working. I seem to remember someone menttioning that there is an official Nikon repair centre somewhere around the Navan area. Bought a SB 900 in its place, and also have a SB 600 but would love to have the 800 back in action. Besides I intend to start doing some off camera flash work and will need at least three or more flash guns.