as far as i needed to, to get it resolved. If our new cars give me trouble i go back to the dealer, if they won;t help i'll go to head office and further up if needed
A new car from a dealer should carry with a guarantee and you should make yourself aware of what is covered in the guarantee.
2nd hand or older cars from a dealership should also go through a mandatory list of checks before being sold and therefore if they play up soon after purchase, take the matter as far as you can until somebody listens!
You have less rights if a private sale as it will be "buy it as you see it"
i would go back to the dealer and have it out with them.
speak to the "proprietor of the dealership" as he's the main person in charge.
tell him whats wrong and what you want doing and if the car "is unfit for purpose" or it has recurring faults (not necasseraly same faults) you can ask for an exchange of vehicle due to the "unfit for purpose" ruling. I have indeed done this myself but wanted the dealer to pay any money on a p/x elsewhere as i didn't want a 2nd car off them and i told my friend 3 months ago to do this and he had his large deposit back and the finance squashed and he went elsewhere. don't let them fob you off, i usually say i'll drive across the entrance so no-one can get in and no-one can get out, but i actually would do it to make my point.