Well, you've posted this under 'Law' but I suspect that you really only want us to tell you what you already know anyway:
IF IT'S NOT GOOD ENOUGH, OF COURSE YOU SHOULD COMPLAIN!!!!
While there may be nothing in writing, a contract still exists between you and the workman. Further, any court would rule that it's an implied term of that contract that the work should be of a quality "which would be acceptable to a reasonable person". You're a 'reasonable person' (I assume!) and you've decided that the quality is unacceptable. Assert your legal rights!
Start by politely pointing out your concerns, and asking that the faults be remedied. Then, if you don't get anywhere, introduce a few phrases such as "I really wouldn't want this to end up in the courts". (It's amazing how often a few vague threats can help!). If things get really nasty, post again and we'll give you some further advice.
Good luck!
Chris