You really should reject the car under the Sale of Goods Act (however, I know that this option doesn't exist forever - you'll need to check exactly).
You have spent a LOT of cash to get your hands on this car - and lets face it, its one of the most desirable at the mo! Long and short of it though, you don't have the product that you have paid a lot of money for. A product needs to be 'fit for the purpose in which it was intended....'. Yours most certainly isn't!
If you speak to your local Trading Standards Office and outline your case, I'm sure you could get some proper representation. I have had loads of problems with my MK4 GTI TDi, and the dealers attitude was pathetic until you went out of the loop and bought the big boys to the table. You say you've got things in writing, this will help put your case across. I doubt very much that any arbitrator in such a case would not rule in your favour! Either that, or give those lunatics on Watchdog a call, might even open some doors for you!!
Let us all know how it goes.
