firstly ignore pauln90's answer, its wrong.
With your parents approval and subject to terms and conditions of their insurance policy you CAN be added to the insurance.
Also you don't have to own a car before you can get insurance, if you have a friend or relative that owns a car, with their consent you can be added to their insurance, again subject to terms and conditions of policy.
You shouldn't have to much trouble providing the car is not high performance, a little ford fiesta/corsa or punto are generally cheaper to insure for young drivers including provisional drivers. Btw I work in insurance so I know what Im saying here is correct.