Waste broker
A Waste broker is someone within the waste industry who acts as middle man between other waste industry parties. They are required to be registered with the Environment Agency.
The client would typically have some rubbish (trash) to take away, and rather than ring round a few contractors in the area they ring the Waste Broker, and give them all the details of what they want. This Broker person or organisation will have a list of those contractors in the area, and it is they who will do the ringing round or emailing, to see who is available to do the client's pickup.
The client might be a producer of recycled materials, and want to sell them. They will contact a Trade Broker who performs a similar function. Usually the Waste Broker is local or at most national, but the Trade Broker could be arranging shipments between countries.
WRAP (definition of Waste Broker): http://aggregain.wrap.org.uk/terminology/waste_broker.html
Who needs to register?
Broker Responsibilities: http://www.netregs.org.uk/library_of_topics/waste/waste_carrier,_broker,_dealer/waste_brokers_responsibilities.aspx
Magazine article: http://www.waste-management-world.com/articles/2012/10/waste-management-brokers-are-good-for-business.html
Scotland: http://www.sepa.org.uk/waste/waste_regulation/application_forms/waste_carriers_and_brokers.aspx
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Wikipedia