The clearly visible lefthand rearview mirror could imply LHD, unless it had mirrors on both sides...
The internal rear-view mirror, mounted on the dashboard, seems to be angled towards a driver sitting in a RHD car. And I believe I can see a vague outline of a steering wheel on that side. As has been suggested, there were numerous GRP bodies available at that time, but I think the coachwork looks like alloy in the way that the paint has faded.
Perhaps Barrett could tell us in which town/city the photo was taken. It was most likely locally built.