As several people have already posted - why not just confront the tiler with the issues you have and ask him to put them rught. He might surprise you and that would save all the hassle of going legal with it. If he won't play ball then speak to the trading standards for advice. The TTA are independent but expensive. The BRE may also be able to help with this. They also independent. NO idea if they cheaper than the TTA or not though.