I'd go him for full money back, plus removal fee's. The only thing he can probably keep is excavation costs. The only hiccup I can see is that you have already paid the price. He will argue that by you paying that you have agreed to the satisfactory completion of the job, but I think if you haven't signed anything, plus the attrocious state he left your job in, you should have a good case against him.
He didnt do any excavation!!!!
Also as we cannot walk on concrete for a few days we could not see the job where all the issues were apart from a distant look or a look out the window.
We are now just waiting 10days for his response, if we even get one then off to court we go. Hi-ho!