There’s no need to panic. Once a new car has been ordered they can keep their existing car for as long as it takes for the new one to arrive – even if that’s 6 months or more. The insurance will be extended and the car can be serviced and MOT’d as normal. It must have a valid MOT when it reaches 3 years old, but when it’s eventually handed back it can have as little as 1 day MOT remaining. They can even extend the current lease by 3 months if they want to take their time choosing their next car. This might be useful as cars ordered in haste often turn out to be poor choices.