if the oil has gone into the wiring loom them just replace the injector harness to remove the problem and then every so often spray cleaner into the plug to remove any residual oil from the harness. Cant see why you would need £ 808 worth of harness fitted. The ECU can be opened and cleaned out quite easily
Had exactly the same problem with the wifes 2001 TD4. Tried cleaning but problem re-appeared. Fitted re-con callipers about a year ago and no problems since