Thanks for all the helpful info. I shall investigate further and update here later.
Further investigation today found it only continues to on dip beam. Switching to full beam kills the engine. The documentation that came with the car shows wiring repairs were done following a mouse infestation.
I don't know if the ECU has been changed but there appears to be no immobiliser, so I believe it has been disabled. I'll look to see how thats been done. I had seen the M16 variant wiring diagram which is very helpful but unfortunately is incomplete.
