Hymer models with Hella headlamps No E 7415 the lamps can be adjusted for left and right hand drive. Although access is not easy there are three screws on the back housing that when loosened allow the lamp to be pushed away from the lens and rotated past a locating stub to the other position. On top of the lamp housing is an indicator (marked L and R) to assist with the direction to turn the lamp. I have found that once the procedure has been completed, the bottom screw does not have to be completely tightened. This will make the procedure easier next time.
Info from Nigel Abbott.