A garage or a motor dealer have to give you 3 months major mechanical parts warranty, its the law they have to do it. Even if the garage states that the car has no warranty they have to cover you against major mechanical faults, if they dont they are taking away your statutory rights and trading standards will come down on your side.
Some garages will ask for an additional Warranty payment for high value or high performance cars to cover less major parts and labour. They simply buy a warranty from another company ( for example the RAC ) and sell it to you at a higher price. Its is well worth looking into exactly what you are getting for your money because with alot of the warrantys, most faults will come under consumables and wont be covered ie tyres, brakes, exhausts, clutches etc.
You would be better off to find a nice example thats not in a garage and save probably £1000 and spend half of that on a decent warranty that you arrange yourself from somewhere like
http://www.warrantydirect.co.uk/quote_page1.html.
Alternatively, if you are confident that you have not bought a lemon, just keep the money you save and use it to fund any repairs in the first 6 months or so. That way you may end up with the whole £1000 left after 6 months.