There's rust warranties and there's rust warranties. The Vauxhall car company made a big splash at this week's Birmingham Motor Show when it showed off a new Astra submerged in 22,000 gallons of sea water and surrounded by more than 2,000 fish. The sea-water test was to show off the car's 12-year, anti-perforation warranty. The Margin's old banger, meanwhile, can't even survive a day on the beach without developing a few new rust spots.