Many people sell Dylon's Dyeing Salt. It generally goes for about £1 + postage. Did you know that it's just sodium chloride ie common salt? You can get 500g of salt for 50p!

Dylon's cold water fix is about 50p for a tiny 15g sachet. It's sodium carbonate. This is also called soda ash and is not the same chemical as sodium bicarbonate (also called bicarbonate of soda).  Soda ash is sold on ebay for a couple of quid for several hundred grams!