Ignore it, where's the proof? (did you sign in agreeance to pay?) They should be covering it all in reality... what's the point of a corrosion warranty otherwise.
I paid it. They did a good job and I only agreed a repair to my boot handle rust. In reality i got a complete new tail gate all new boot hatch mech and they honoured the original quote so i cant complain!
Yeap good on you (I mean that), I admire you paying for what you owe to the people who do the work... but the payer should really be VW; standing by their guarantee in full, sadly they are not as honorable.
I had the same work done in April, two new wings and a new bootlid. I was lucky enough that the garage I went to covered the other 50% as vw UK were also only willing to cover 50%.
So I got all in all, two new wings, new bootlid and a new bootlid badge as the last one was corroding.
It really depends on the garage and how helpful they wish to be.