Neil,
I had to wait for several years to get this stage of soil like yours!
I started my garden in summer 2010 on weedy, rock hard clay soil. The same tragedy on 300 m2.
I began to dig and stopped after a few minutes. Tried it never again. In the first two years it was not possible to sow any seeds, just planting seedlings. The solution was compost and more compost. And cpmpost again!
Happy gardening!