No earlier than your third letter or e-mail, mention that you are 'prepared to consider legal action' although you 'hope matters can still be resolved amicably'.
Don't play this card too quickly because it can burn bridges but, if a settlement seems unlikely, then such a warning will make your complaint a priority.
For disputes over new and used car purchases, the most important legislation is the Sale of Goods Act 1979. Under the Act, goods must be:
• As described;
• Fit for any purpose made known to the seller;
• Of satisfactory quality;
• The seller's to sell.
In the case of a new car, that means you can expect it to be free of defects. A used car won't necessarily be perfect, but should be of a standard that any reasonable person would expect, though exactly what that means would be up to the courts to decide.
Any new or used car warranty is in addition to your consumer rights and can't be used to limit them. So if a used car comes with a month's warranty, and it breaks down outside of this period, you can still try to seek redress under the act if the fault is serious enough.
Rejection, refund, repair or replacement
If the car does fall short in one of the four terms above, there are remedies available.
The one consumers love, and dealers hate, is 'rejection and full refund'. Dealers very rarely accept rejection without a fight, and the clock is ticking from the moment you collect the car: although not defined in law, realistically you have just two or three weeks to reject the vehicle.
Time is on your side in one respect, though. Any problem that occurs within the first six months is assumed to have been present at the time of sale, unless the dealer can prove otherwise.
Repair is usually the dealer's favoured option, but the Helpdesk mailbag is full of letters from owners who keep going back to the garage with the same fault.
The act states that repair should 'not cause significant inconvenience to the consumer'. If it does, then aim for a partial refund (say, the car's current retail value, not trade-in value) or a replacement (a car of equivalent age, specification and mileage).
If you bought your car privately, the act doesn't apply, but a car should still be 'as described'.