We got it sorted finally. Replacing the immobilser control unit restored the communications at the OBD port, apparently the diagnostic connection goes through the immobilser. The ECU was re-coded but still cranking with no start. The coil pack was changed and she started up. No trouble codes in the ECU. So to summarise, the problems were caused by three components becoming faulty at the same time. The ignition switch, the immobiliser control unit and the coil pack. 2 days labour plus parts... ouch. She was going great for a day until the MAF sensor failed, but that's a different story....