Ozzy – too late for this year, but in past years I’ve top dressed no-dig beds with horse manure from stables in late October – late November and it has been perfect for growing potatoes in the spring. I’ve done similar for where I”ve sown peas in early March and asparagus grew superbly in the spring after coating the bed in late autumn. It doesn’t seem to harm comfrey or rhubarb either.
If you’re starting now, it may be worth building a big heap to let the heat generate quickly and then, once it’s cooled down top dress your beds?