Unless they "default" on the agreement. I cancelled a 12 week "contract" with an estate agent 6 weeks in. I wasn't getting many buyers through the door and when i questioned it they told me no one was interested and that it has been "very quiet". I got a couple of my friends to ring up and pretend to be a potential buyer without specifically mentioning my house, just the locality. My house was not offered once. Needless to say i was on the phone straight away and dispensed with their services.