What is the difference between bio and non-bio?
Biological contains enzymes that break down protein and food marks at lower temperatures. Non-biological leaves the enzymes out and is the usual choice for sensitive skin.
Are the big refills better value?
Considerably, per wash, and they save a great many bottles. Decant into something smaller for everyday use.
Will these work in a cold wash?
Yes, at 30 degrees for ordinary washing. Heavily marked items and towels still benefit from a hotter cycle.
Do you sell fragrance-free laundry liquid?
Bio-D and parts of the Ecover range are the plainest. Check the individual product page, since formulations vary within a brand.