Andy im in the same boat as you, started S3 shopping and had all sorts of problems finding one, contacted the factory and asked if they had fixes for the issues and they basically told me i should buy a new car.

So i asked them if they had tested the new cars to a standard where they could give a warranty at a similar level to some of the cheapest cars on the market, like a aygo or panda (~9k). There was alot of squirming.

So i offered to test it and help them get to that level. I would use it as a commuter (between UK, Norway and Poland) and pay for the fuel, tyres, brakes and they throw in the car. They get to keep the car for 1 week in 3 and i would put 2000miles a week on it for them. If the car could keep up for a year i would buy it.

Interms of the other manufactures. Defenders leak and corrode, but they do a different job, and in all fairness, im pretty sure between me and the father in law we have abused his over the years, for pulling boats and cars on trailers as well as getting in and out of the village in the winter.

Golf platform cars have problems with the pollen filters leaking.

MMC seemed to have forgotten about how such troubles killed lancia in the uk 25 years ago. Customers now expect that there wont be any bubbles on there cars for 8-10 years. What scares the hell out of me is they have teamed with Magnesium Elktron for the EvaGT, and Mg will be worse than the Al that they use at the moment for corrosion.

http://www.magnesium-elektron.com/data/downloads/Corrosion%20Protection%20Principles.pdf

Whats the most frustrating as you say is the technology exists, I would happily make twintex wheel arch liners for MMC in our factory in poland. Infact if we can find 20 people who want them i will tool it and make them for less the the cost of an average aero service.

May be TM should do the R&D which MMC seems to be missing!