I Know nothing about Diesels, but here are a few notes picked up from the Facebook Forum
The car doesn't switch off with the key, anyone have this fault before, guessing ignition switch.
The 1.4hdi is a common rail diesel having electronic injectors. There isn’t a stop valve on the pump, but a prop valve or regulator which looks similar but isn’t. When the ignition is turned off the injectors are shut off so check the ignition switch or more likely the main relay sticking open.