To be honest mate, I have had a "friend" do a job in my flat and it was shit. I didn't like it but I gave him two chances to sort it and he didn't so I told him where he could shove it basically.

When hiring anyone to work for you always, always write a contract outlining the work the be done and the costs involved and agreements on how much to pay up front and home many installments have to be done and what the final amount to be paid will be. It will also mean that you can put in there if your not happy with the work you can withhold the money until its done properly even if they say you have to pay them.

I'd sack him to be honest mate, get shot of him as soon as possible and get someone else to sort it. Make sure you get references and you sign an agreement!