My sister and B in Law have stables in Surrey and a HUGE pile of well-rotted horse manure. They would be glad of the space (I'd love to attack the pile, but it's 60 miles door to door and we can get well=rotted one mile from home). It's free to anyone who wants to bring their own bags/trailer and take it away.
If anyone's interested, PM me and I'll let you have the address.
:) :) :)