Tesco in Lewisham have a range of wines at half-price. Not the usual overpriced stuff that is regularly half-price, but some nicer wines. I bought Tesco Finest Vouvray, Tesco Finest Alsace Gewurtztraminer, Redwood Creek Chardonnay and some organic Pinot Grigio, all at half-price. They also had more expensive wines, discounted by 20% and more.
Hopefully it's nationwide - they had proper shelf-edge labels showing the discount.