You have the right to reject this vehicle, as it is under warranty and is clearly not of sufficient quality if it needs immediate repairs and will be off the road for several months.

It is likely that the dealer will have already sold on your part exchange vehicle, so they will not be able to return your old vehicle to you. You can ask them to supply you with another vehicle of equivalent value to your new car instead of waiting for repairs or rejecting the car outright - this may be the best solution as it will get you back on the road as soon as possible.

Write to the dealer and send your letter by recorded post, explaining the situation, why you are unhappy and what you want them to do to rectify the problem. Be aware though, this could be a lengthy and time consuming process.