Thanks awair.
I'm looking at 3 possible tracks
1) A clarification from the FAA to my request (already submitted) that they cite the regulation which the DPE has used to deny my application
2) Have discussed with a US CFII about going to a different DPE
3) Doing a US Private licence written and Flight Test
I do not anticiapte the FAA has the ability to provide a quick answer, so I'm guessing option 2) or 3) will come into play.
But I would like to get the FAA and the DPE to show the documentary proof.