There are two relays in the box under the bonnet, one brown one black and they are side by side. They are responsible to change over the beam and flash IIRC. Pull them both out and check the connections in the fuse box, and then plug back in. I cannot remember if the ignition has to be on (my dashboard is out at the moment) but with it on just in case, have someone hold the stalk in the flash position and move the relays about, you may catch the headlights flickering. This is becoming a well known fault on the 80, the contacts normally burn and stick on the black relay, I always replace as a pair.
Given the dashboard light comes on tells you the stalk is doing it's job, so the relays would be the next port of call.
regards
Dave