You will never get a penalty in the UK for smoking in the car
We want to remind about not old changes in the smoking law. Wales was the first who banned smoking in a car carrying children. England followed their footsteps on 1st of October, 2015. Scotland could be the next to follow this law. The fine of not obeying the law is £50. The law only works for people travelling with children. In other scenarios, no one will get the penalty. However, smoking in a convertible car with children is allowed.