My recent search in Tesco found no white grape juice at all, but red juice was available in the chiller for £1.50 per litre. Wilco had some concentrate at £3.00 per 220g but no Young's Definitive, which is a slightly better deal. Minced 'value' sultanas are still the best option. I recently found an inexpensive 'low grape' recipe, which I have modified:
150 g sultanas
2 litres apple juice
1 jar of 'value' honey
A handful of dried elderflowers
5 g tartaric acid
5 g tannin
1 teaspoon pectolase
10 g oak chips
Yeast and nutrient
Sugar (about 500g) and water to 5 litres and sg 1090
Mince the sultanas in a food mixer with some of the sugar (makes it less sticky). Add to bucket with honey and elderflowers and pour on some boiling water. to release flavours and dissolve sugar. When cool, add remaining ingredients, except oak chips. Strain after 3 days. Once pulp has settled, rack into fv and add oak chips. Continue fermentation at 15 c. Rack again at sg 1005, rinsing the chips and putting them back in. Once fermentation is complete, allow the wine to sit on the sediment and clear naturally in a cool place. Once clear, rack again and leave with the rinsed chips for a month, then bottle and leave for 3 months or more.
The bouquet will be much improved with fresh, rather than dried elderflowers, while the flavour would be further enhanced with a higher proportion of honey.
Although this is basically an enhanced apple wine, I recently tasted an excellent £8 bottle of French Touraine sauvignon blanc, which tasted of honeyed granny smith apple with a floral bouquet. It was very dry, with a ph of 3.1. It went down a treat with wild salmon, oven baked with lime slices and parsley.