Rogue traders (or cowboy builders) trick people into spending a lot of money on building work which is either poor quality or completely unnecessary. They may even take your money and not carry out any work at all.
Never let people who turn up unexpectedly at your house do any work for you, and never agree to buy anything from them. If a deal sounds too good to be true, it probably is.
Agreeing to buy a product or service from a trader you don't know can have serious consequences for you, your home, and your money.