Legally, anyone driving a vehicle should hold a valid driving license for that category. As the owner, it’s your responsibility to ensure that those with a valid driving license are driving your vehicle. Also ensure that no one (including you) drives the vehicle under the influence of alcohol or drugs. If the driver is intoxicated at the time of an accident then insurance company is not liable to compensate the policyholder.
Type of car: If you have an expensive or powerful car then you are seen as a higher risk for a number of reasons. If it’s expensive, it has a higher risk of being stolen. If it’s powerful, it’s deemed more at risk of getting into an accident driving at speed. If you want to see how your car impacts your insurance, you can check which insurance group it’s in for an indication.