I like the bit "Not obtain work through cold calling"

Checkatrade members agree to:
Be honest in all dealings with you
Tell you about any call-out fees before coming to you
Let you know straight away if they can’t do the work
Keep appointments and arrive on time (calling in advance if they need to reschedule)
Be realistic about when they can start work and how long it will take
Be courteous. Treat you, your property and belongings with respect
Keep you in the picture about all aspects of the work
Return phone messages promptly
Create an additional contract for variations from the original agreement
Deal with complaints promptly and professionally
Never demand cash payment
Never be verbally or physically abusive or threatening to a customer in any way
Not obtain work through cold calling
Checkatrade members will give you a feedback card up front. After they have finished the work, send it in to let the public know how they did. If you prefer, give your feedback online.
http://www.checkatrade.com/Consumer/CheckatradeStandard.aspx