I'm very sorry for your situation. It reads to me as if you have been switching off the engine while the DPF was actively regenerating using post-injected diesel. Instead of being burned in the DPF some of the post injected diesel has sunk into the engine oil sump, contaminating the engine oil and raising its level. Once it gets past a certain point, being a compression ignition engine, the engine can run uncontrollably on the oil/diesel mixture in the sump. But if the engine starts, then a proper oil service (possibly including removal of the sump to get rid of all the contaminated oil) should sort it out. This shows you local servicing garages, including Hofmans of Bicton: good-garage-guide.honestjohn.co.uk/directory/searc...g / I think the mechanic is being honestly cautious about giving you a price because he is not sure of what damage occurred and the same would probably be true of any garage.