So heres the response I've just had from VWUK....
Dear Mr Gallagher
Following your email dated on 16 April regarding the corrosion on your vehicle, I can confirm the outcome of my investigation. I am sorry for the delay in my written response.
I appreciate that your expectations of reliability and build quality are high when you purchase a Volkswagen and that any failure is most disappointing. However, as with all manufacturers, it is always possible for an issue to arise during a component’s lifetime. It is for this reason that all new Volkswagens are supplied with a comprehensive three-year manufacturer’s warranty or 12-year body protection warranty.
The 12-year warranty covers corrosion that begins inside the vehicle’s body and works its way out. West Bridgford Vertu Volkswagen has confirmed that the issue with your vehicle arose because the protective covering of the paintwork of your vehicle was compromised. This allowed water to penetrate under the paint work, causing corrosion from the outside in. The issue is therefore not covered by the 12-year warranty. It would have been covered by your vehicle’s three-year warranty, which has now expired.
When the warranty on a vehicle has expired, our retailers are empowered to look into a goodwill gesture if they feel it is appropriate. In order for them to do this they will need to diagnose and repair the vehicle. We cannot overturn their decision.
I appreciate that this is not the response for which you had hoped, but trust that I have clarified the reasoning behind my decision. Thank you for contacting Volkswagen UK.
Kind regards
Feels like a fob off to me, not really sure what options I have now....apart from get it done myself