Fixers: Not an official position, individuals are recognized as fixers based upon their history of being able to get things done. You know you're a fixer when people get referred to you when they need help.
In general, fixers have a solid grasp of the Whateley Academy Student Handbook, are personable, have agile minds, enjoy helping others (which results in favors being owed and connections established with a large number of students/staff), are confident and of strong character. An inquisitive nature, the ability to coordinate things and get people to cooperate, the knowledge to game the system, and the finesse to get things done without getting anyone on your case.
For practical reasons they do establish turf, and refer people to other fixers if it would be appropriate; while not as tightly organized as the campus bookies network, they know who their peers are, and cooperate with each other. Each cottage page lists their Fixers, and this page lists them all.
They're not fools, they do check to see what's going on before giving their help, but once they agree to help, all their considerable resources will be bent towards the task.
As stated, Fixer is not an official position, and is not recognized formally by the Whateley Administration. As a practical matter, Administration allows students to have someone represent them, act on their behalf, provided they are knowledgeable and respectful and work within the established structure following proper procedure. Conversely, Administration may, when needing help on the fly, co-opt Fixers to assist in the task at hand; co-option by House parents is the most common case.