Geoff2,
You should try to claim under the mobilo warranty as the others suggest. But a word of advice before you take it in. You should examine the whole car very closely and find all areas of rust, however small, especially around the tailgate and move the rubber back around the tailgate lock. The cross members on the bonnet are a good place too. The dealers will only submit a claim for what you point out to them. Also check the quality of the re-spray very closely and don't accept it until perfect.
My car went in for warranty work at the begining of October for 3 weeks, where they: put on a new bonnet and a new passenger side front door, and painted 3 out of 4 wheel arches, along with the remaining three doors and the boot lid on my 2000 E320CDI saloon. I have taken it back a couple of times as the finish hasn't been perfect, which has resulted in the bonnet being re-painted, and the whole car being re-laquered. I finally picked the car up again last Saturday only to find a small chip on the front wing and black specs under the laquer on the boot lid. I was also gutted to discover another rust spot on the rear of the passenger side sill. The car is going back again on Friday for the paint to be put right, and the "new" rust to be rectified. They must have seen the sill corrosion in the bodyshop, but were not "allowed" to do anything as I hadn't already raised it.
So, check everywhere carefully and good luck.
Mark