If they try and refuse to do this, its very simple.
Whenever you talk to them, stay calm, moving towards stormy by the end of the call. Keep them on the phone, even if you have to go silent for 30-60 seconds at a time when you reach an impasse. People hate silences and start saying stupid things. For some reason - silence builds presure like you would not believe. (Its a japanese technique).
Next thing to do, ball out the pratt your speaking to. When you've had enough of them say this to themdirectly "your pointless - let me speak to your manager".
You now get the manager. Do exactly the same thing to him. Until you get absolutely nowhere or he relents. If you get nowhere - speak to his manager.
Now, heres the key. No one wants you to speak to their manager. It makes them look bad. So if the manager of the whole garage then has a customer yelling at thier area manager - it makes them look bad. If a director of the company has a pissed off customer, it makes the area manager look lame.
And if the director cant help, ask him for VW head office number and speak to them. omeone authorised the repair to your car under warranty. Follow the chain. He will then look bad in front of the VW and so forth.
You climb the ladder for as long as you want until you get what you want.
If you get all the way to the top, threaten them that you will speak to Topgear producers, and explain your exsaperation to them.
You wont get that far. Its cheaper to repair your car than look bad in front of "their" boss, whoever that may be.
Works for me everytime. Last victim was Kwik Fit and I got a free tyre out of them.
Tin