I got used Mango Chutney barrels from a local Indian restaurant. They are thick plastic and hold about 20kg each. So perfect for me as you can move them around and stack them. Working well for 2 years. I actually bought them from a guy who had collected the old oil from the restaurants to make into bio-diesel. Paid £2 per tub.
On a bigger scale, an IBC with the top cut off works well. A cubic meter of storage for about £20 2nd hand.