This is a non-start since the battery ran down (It was fine before)

It cranks immediately on pushing the "Start" button (IE there does not seem to be any glow plug operation) and will crank until the button is pushed again to stop it.

I seem unable to get the ignition to come on to check for fault codes etc.

IIRC I should be able to do this by pushing and holding the start button without depressing the clutch.

Repeatedly pushing the button will bring up the aircon display but not the dashboard.

Am I missing something simple here? any suggestions?

Paul