Last year's delicious wave of super cheap Marlborough SB seems to have abated but I noticed ASDA have a 2010 one in their 3 for £12 deal (sadly 3 for £10 has gone). This is usually an £8 wine so well worth seeking out. If you haven't tried NZ Sauv Blanc you have a treat waiting.
Got half a dozen and looking forward to giving it a try when it's chilled!
UPDATE: Just opened one (well, two actually) and it's REALLY good! Lots more fruit than many of the cheaper NZ Sauv Blancs; quite dry really with some grapefruit in there somewhere. Well worth trying - I'll be chasing some more asap, hope the stock lasts.