The Free Tree Scheme sounds interesting - I must Google it.
The grindings from the stumps should be well-rotted by now and will have put some goodness into the ground, but I agree with Rusty on prep.
The other problem with new hedges is weeding, where you can damage the roots of the whips when they are young. If the ground is weed-free I'd consider a weed-suppressing membrane and planting the whips thro it and then mulching with bark chips or something to cover it up.
It you click on the "hedge" tag at the top of the page there are lots of posts which might be useful.