English car abandoned at home (France)

Therefore, it is probably legal and not abandoned. Generally, the UK police (as in France, I presume) will not act unless the car is on the road illegally, i.e. untaxed, uninsured, parked precariously or causing an obstruction. If the manner in which the vehicle is parked is causing inconvenience to the homeowner (which should be yourself. Third party complaints will not be accepted as a rule) then take a photo and present it to your Police, they should then contact UK police to trace the owner and get the car moved. If the vehicle isn't insured the police may remove it anyway but I'm not familiar with French procedures.