TheScullster asks:
"If I go with horse, how long do I have to leave it to break down before
digging in?
I intend to use it to rejuvenate a border from which we are removing Laucon
firs.
Probably replace firs with hedging - pyracantha, laurel, escallonia etc"

My book says 2 months ... and 12 months for cow manure.