I've just come back from Tescos with six 3 litre boxes of their own-brand Californian Red.
The normal price is £13.89 a box but these boxes are currently on offer at £10.00. If you buy six boxes you qualify for an additional 25% off. This drops the cost down to £7.50 per box which works out at £1.87 a bottle. That's extremely cheap for wine these days!!!
I haven't tasted it yet but it's got 12% alcohol in it and is (probably)made from grapes so it definitely meets all my exacting requirements!
PS - I did look for this on Tescos wine website but could only find it in bottles (and they had none in stock anyway)
PPS - there's also a matching Californian white wine 3l box which is exactly the same price deal as the red.