hi mate,
i'll try and help you out ...
firstly can i say that if you wanna spend 12k on a polo you go for it mate, it's your money and your effort at work that pays for it.
if you want a polo then i'd say instead of buying brand new, consider one which is preregistered, this basically means it's brand new, but has been registered so will be about 1k cheaper
another good option is to buy a car that is a couple of years old, which has been serviced at that garage, so you can ask them about what has gone wrong etc. this will give you some peace of mind aswell as saving you probably £4k on your choice of polo.
i will say now that spending £7k on a car for three years and not having anything to show for it is not advisable. if you want to buy the car new why not buy it on hp so that you have some value in the car in three years time, i.e instead of giving the car back you would be part exchanging it, and if you buy well can reduce the amount you pay in the future.
getting money off dealerships is quite straight forward, even for VW's (think there's abit special) all you have to do is go to more than one VW dealership in the area, get a price and make sure they know that you are going to smithkightfay (example) and also how much you've seen one on the internet but would like to buy face to face. if you say live in manchester, go to the 5 or 6 dealers there are around and ask them for a quote. they know there's competeing with the others so should give you a good price.
then go to the second cheapest and say the cheapest where doing this price and throwing in free servicing for three years, see what they offer you.
so in summary, buy one brand new by all means, but i'd advise against the (hand it back option) becuase you could just part exchange your car (it's the same thing but enables you to use the residual value in your car)
lastly i'd say you've been really unlucky with the car you've bought and spent 3k on in repairs, and i can understand your reaction to this, but please be aware you are just peed off with your experience. french cars are not the best made, but shouldn't go that wrong really. a vw should be more reliable, as will almost any other car, so try and trust the brand and get one that is a few years old, with brilliant history etc. you have the money to be very picky, if you want a polo get one, no probs, you could have all the toys, biggest wheels going etc, but in a car that will be worth something in the future, and if you experience any finacial difficulties in the future wont force you to keep on paying the monthly payments.