Well I did get a reply from the ORR and here is the relevant section.....
"
We are advised by our Enhancements team that the station platform was not brought into service as the independent safety assessment body had rejected the Network Rail submission, and the none compliant construction tolerances had also not been accepted by the standards owner, the Rail Safety and Standards Board (RSSB). A positive assessment from a UKAS accredited assessment organisation is required by law. Therefore, for these reasons, ORR were unable to process the authorisation to take into service. We are still waiting for a complete and compliant submission from Network Rail.
....so basically NR say it is the ORR and the ORR say it is NR....meanwhile the long suffering customers still have the inconvenience of a short southbound platform three months after it was, to all intents, finished!