I have made the wilko cabernet sauvignon and it was totally undrinkable until it was 3 months old when it suddenly became quite good. Also have loads of there pinot grigio in bottles at the moment and its getting better but I am not to impressed at the moment, I would say its as good as some of the cheapest commercial wine and its around 3 months old now (when it was very young it was not as undrinkable as the CS). Adding grape juice (or concentrate) will improve the body of the cheap kits, I think in the youngs case its in 2 sizes and you add the smaller one to a 6 bottle youngs kit in place of sugar and the larger one to a 30 bottle kit. The oly other kit wines I have done are the beaverdale range which are over twice the price but I think you get what you pay for in terms of the end product.
If you want cheap & ready to drink fast I recommend you try fruit tea bag wine as described here -
1 Box (20) Fruit 'Tea Bags'
2 litres Grape Juice
2lbs sugar (or thereabouts)
1tsp Citric Acid
1/2tsp Grape Tannin
GP Yeast & Nutrient
I've used 1 box Twinings Cranberry, Raspberry & Elderflower bags and Sainsbury's 100% Pure Pressed Red Grape Juice (not from concentrate, no preservatives, 3 for £2) but you could use any fruit infusions bags and red or white grape juice as appropriate.
Infuse the bags for 30 minutes in 2 pints boiling water.
Boil 2lbs sugar (or thereabouts) in 1 pint water.
I measured the SG of the grape juice at 1.068 and calculated that 1lb 12ozs sugar would give an OG of 1.110, and have read somewhere that boiling the sugar inverts it and makes it more fermentable.
Wring the bags out as best you can without splitting them and pour infusion liquor and sugar syrup into a bucket, add grape juice, allow to cool, add Citric, Tannin, Nutrient and Yeast and let it rip. After the initial whoosh has subsided, pour into a DJ and make up to 1 gallon.
Dead easy, and I cost that at around £3.50 per gallon or 60p a bottle at around 13% ABV.