just had a quick look at the article,one of the reasons for this is down to the scrappage scheme for purchasing new cars,quality used vehicles became scarce and garages were selling anything they could lay there hands on to survive. High mileage & older vehicles that a few years ago would never have been on a forcourt ,they would have gone straight to auction, this includes main dealers.
I have seen main dealers selling vehicles called 'runarounds', 3 months warranty and under £3,000 again a few years ago it would never have happened..