I swapped over a few months ago and now I always use value brand bio washing powder and fabric softener, have tried Asda and Sainsbury's version, no difference between the two, as far as I can see. It isn't quite as good as top branded stuff in a quick wash (which is the program I use as uses less electricity), so every so often I use the long program for a week just to spruce things up again. Occasionally need to use soda powder or vanish, but over all for the difference in price I doubt I shall ever pay op price for washing powder again - even when I do start earning a good wage again.
AFAIK, 1 kg = 65p, 3 kg = £1.67
1 ltr softener = 49p
Also sainsburys value baby bath is about 22p, I probably wouldn't use it for a baby's bath, but is great in mine and the childrens' and value soap, 14p for a pack of four bars - again it's great stuff, their basics potatoes are £1.49 for 5kg, and sainsburys value chocolate is delicious... (I am still finding my way around the value ranges of Asda, sains burys and tesco...)