I'm pretty sure it's considered trespass if you have a sign that says 'no hawkers' or similar. Legally anyone can knock on your door, UNLESS you've told them to go away, either by a sign or verbally. Then they must leave. I feel really sorry for most of them, they have an awful job. I don't have a sign up, but we were just getting the same energy company sending people and i told the last guy to make a note not to knock on my door or I would speak to he company. He was really scared and said 'please Miss, don't make a complaint about me' poor bugger is just trying to make a living.