I have a feeling there is a long thread on this somewhere,. but basically after a lot of research I bought a large strong lidded dustbin. Put some brash (it woody twiggy stuff) in the bottom then a shovel full of garden soil and a kilo of good big dendrobaena worms, you can buy online or from a fishing shop.
Then just fill up with poo.
When full - which will take much longer than you think as the worms will be eating it and turning it into soil, leave for a year then use somewhere you wont be handling it, ie not on veg or pleasure gardens - really thats just to be on the safe side. It will look and smell exactly like normal earth