Seeing as this thread really helped me I thought I'd contribute.
So my fiancee's MK5 R32 has bubbling front arches. I took the car to Blade Accident Repair in Gloucester, fortunately I'd found this thread previously whilst doing some research and was on the front foot when dealing with a man called Mike Holiday.
I showed him to the car and he proceeded to take some paint depth readings, the results were 174 microns on the passenger side 155 microns on the drivers side - he said the readings were too high and he wasn't going to process a claim.
Believing that the car had seem some paint I resigned myself to getting some private quotes for both wings being done. prices ranged from £750 for non OEM parts to £1k for OEM wings. However due to the negative comments in this thread about Mike and Blade in Gloucester I thought I'd dig a little deeper. So I emailed and tweeted VW UK asking what the factory paint depth should be. They replied with 70 to 150 microns, so with the drivers wing being 5 microns over that reading I didn't see any reason that wing shouldn't be covered under warranty. So either Mike Holiday at Blade in Gloucester didn't know what the paint readings should be or he couldn't be bothered to write the report and submit it to VW. Non the less he nearly cost us a grand that we didn't need to spend...
I didn't want to take the car back to a Blade franchise for a second opinion so I took it to a different franchise, South Hereford VW and they were FANTASTIC! Instead of taking a few paint readings they did the whole car, marked out the areas of corrosion took loads of photos. Their readings came out at 143 microns passenger side and 147 drivers side the chap believed that the bonnet had been resprayed at some point and some overspray had landed on the wings so he saw no reason why VW wouldn't process the claim.
Low and behold 2 days later we get a call saying VW will cover it 100% and the cars booked in for May.
Hopefully it'll all go well and I'll confirm once the works done but what a nightmare... Once the work has been completed I'll be submitting a formal complaint against Mike to Blade and to VW.
If you need friendly, honest and experienced advice South Hereford VW are a good place to go.