corsa turn indicators only working on left side - bulbs ok?

fault is probably with the hazard light switch itself, disconnect and attempt to operate the lanterns.
If they illuminate successfully on left and right turn signal then thats the problem.
Or it could be the indicator switch itself is faults, bad earth. Push relay into fuse box to ensure it is tight .

If none of this works then simply offer your arm out of the window when turning right or only drive around Slough or Southhall where nobody uses indicators

Osama fullupwastepaperbasket (bin-laden)
November 2008