I’m having problems with a builder I employed to build a kitchen extension to our house. The foundations are laid, and he’s knocked through the back wall - the back of our house is now a tarpaulin sheet. We paid an initial deposit upfront, and then two further amounts in cash for materials. He’s now asked for more money - but I’d like to see more work done first. We had a bit of a row, and he hasn’t turned up for the last two days. What should I do next?