Hi Watts,
Yeah good point re price. I had priced job at Halfords and PP GTI Vented rear discs and Pads are not cheap to replace. So for a bit more may as well go VWdealer route.
Think reason for a lot of wear on rear brakes is rust, the car sits for a month or more, so the discs get very rusty, and never quite get rid of the rust on rear discs.
I have a BMW Motorbike and had to replace rear disc at 7500 miles due to pitting with rust.