What happens if I want to return the car more than 14 days after taking delivery? 

After 14 days has passed since you took delivery of the car, you no longer have the right to automatically return the car without specifying a reason. You’re still protected under the Consumer Rights Act 2015, but this only allows you to return the car if it can be demonstrated that it isn’t of satisfactory quality, is unfit for purpose or isn’t as described.