Jason, if there were problems with his work, and you had given him the opportunity to fix himself, and he didnt, then I would deduct the money it cost you to fix from the original figure. If I were in your shoes I would go to a solicitor and get a form drafted which the builder can sign saying he accepts 'X' figure in full and final payment of all/any debts outstanding to him. Then I'd go with my form and cash ( not advocating defrauding revenue here, just that people find hard cash extremely hard to turn down, especially at this time of year) and arrange to meet him, have a chat and point out that you had to get such and such fixed, it cost you so much, but that of course the man must be paid for his work, and you make it 'X' inclusive of interest ( give him a bit of interest) and say you have it here in cash if he will sign the disclaimer. Be prepared to walk away if he doesnt accept. But try to keep it amicable.