M&S have got 25% off when you buy two cases just now, delivery is about four quid or free if you spend over £50.
Bear in mind most of the wines on offer are available in store, so easy enough to pick up a bottle or two to try before piling in with a good sized offer. The deal doesn't include every wine, so check the site first.
http://www.marksandspencer.com/l/offers/buy-2-save-25-on-wine-and-champagne-casesJust noticed that Tesco are supposed to be doing the same. May not be available in Scotland though if its delivered from a branch.
JF