Which is the champagne bargain?

The UK pre-Christmas supermarket champagne wars are hotting up. See members'  forum for comment on Morrisons supposed special deal on half price Bollinger, for example.

Today, their rivals Sainsbury's have full page ads in the UK national press touting four different  non-vintage champagnes at £14 a bottle:  Lanson, Heidsieck Monopole, Piper-Heidsieck and their own label Sainsbury's Blanc de Noirs.

While Morrisons seemed to run out of their champagne bargains remarkably fast, one would hope that Sainsbury's will have decent stocks of their own label Blanc de Noirs from a co-op in Reims.  I would recommend this strongly as tasting considerably...