Yes, good point, hard to see from the original photo but the nut is the right way around.
I've removed the nut and there was a bit of glue next to the fretboard that didn't help but it wasn't the root cause of the problem.
I made up a 1mm aluminium shim and glued it onto the face of the nut. Perfect! problem solved.
So all I can assume is that I got a Friday afternoon model, it is definately out of spec. It's a mystery...
Cheers all
Pete