At present tesco are offering 25% off when you buy 6 bottles of wine, but as far as I can tell that's instore only. Online here's the best deals I can find:

Hardys Crest Chardonnay Sauvignon Blanc (750ml) in Tesco | mySupermarket
Oceans Edge Sauvignon Blanc (750ml) in Tesco | mySupermarket
Ogio Pinot Grigio (750ml) in Tesco | mySupermarket
Castillo de San Lorenzo Rioja Reserva Spain (750ml) in Tesco | mySupermarket
Ernest & Julio Gallo Five Oaks Cabernet Sauvignon Shiraz (750ml) in Tesco | mySupermarket
Hardys Crest Cabernet Shiraz (750ml) in Tesco | mySupermarket
Ogio Primitivo (750ml) in Tesco | mySupermarket
Tesco Finest Kulapelli Cabernet Sauvignon Carmenere Chile (750ml) in Tesco | mySupermarket
Hardys Crest Rosé (750ml) in Tesco | mySupermarket
Ogio Zinfandel Rosé (750ml) in Tesco | mySupermarket
Codorniu Brut Vintage Cava (750ml) in Tesco | mySupermarket
Codorniu Reserve Rose Vintage Cava (750ml) in Tesco | mySupermarket
Freixenet Vintage Especial Brut (750ml) in Tesco | mySupermarket
Freixenet Vintage Especial Rose Cava (750ml) in Tesco | mySupermarket
Hardys Crest Sparkling Rose (750ml) in Tesco | mySupermarket