Okay I am prepared to be flamed as there are cheaper deals on champagne out there. Quite looking forward to it really, but I like champagne and I think that Lanson or Moet are easily worth the little extra over the lesser names that supermarkets sell for £10. If you too are fussy then ASDA are selling Lanson Black Label for £15, Moet for £20 and Feuilatte for about £18 all of which are really good deals for pretty good champagne. As I can't find a decent deal on Tatti or Bolli I'll be buying the black label this year.
On-line and in stores.