The central locking on my 1994 GS300 failed on the offside rear door.
Investigation showed that at least 3 of the wires inside the gaiter at the
door hinge had broken, and at least 2 others had cracked insulation.

Is this an isolated fault, or has anyone else had the same problems. I'm
slightly concerned that it may present a fire hazard, and haven't looked at
the other doors yet.

I had imagined that the cables would have been specc'd for the opening and
closing of the door, so am rather disappointed.

I had the same problem on my 1990 Camry. I replaced two wires, but the
remaining wires continued to fail. I had to replace the entire wire
harness. I don't think there is a fire hazard, but I recommend
replacing entire door harness, than fixing each wire.