My Father died recently and the Company has cancelled his coverage. Although I live there (part-time) I am told the house is no longer "owner occupied"

I just went through this recently when being licensed. After a property has been vacant longer than 60 days the insurance company sees this as a potential problem and will cancel your policy immediately.
I would suggest either moving into the property, renting it, or selling it. It is more difficult to prove this as a vacation or secondary home, but that is an avenue you would have to discuss with your local insurance agent.