I'm going to try make my own washing powder again, last years trial recipe wasn't great so I've searched the 'net again and found a new one that seems good.
6 oz soap (flakes or whatever soap I have, but avoid synthetically perfumed ones),
2 cups borax and
2 cups of washing soda.
(All available at hardware stores, some chemists or supermarket)
Finely grate the soap (if not using flakes) and add to the other two ingredients, mix well, and store in a cool dry place. You can grate the soap by hand, or put it through the food processor, but make sure to wash it thoroughly afterwards.
I'll be trying it later this week