Here is a link to the Jeremt Vine show for those of you who missed it. Martin Lewis discusses the tricks retailers use when discounting wines.
It suggested that as champagne is a slow seller during the year the traders whack the price up only to 'reduce' it at times when it sells well like Valentines or Christmas. Obscure wines are put on offer so the customer cannot compare with other sellers.http://www.bbc.co.uk/programmes/b00w78r1
Fast forward to 1:09.29 for interview with Martin Lewis from MSE on discounted wine.