During the term of an HP agreement the car will be owned by the finance company. This usually means bailiffs cannot seize it, but the law is complicated around this so however the law is complicated on this matter and they may suggest that they can. In this scenario contact Citizen’s Advice for help and in the meantime, you may want to consider moving your vehicle to a different location where bailiffs are unable to access it , for example, a friend or family’s driveway (assuming you have permission) or a locked garage.