The association is run as a not-for-profit company limited by guarantee. It’s day-to-day activities are controlled by a council which is elected by the full members (see membership) of the association. The council performs the same duties that a board of directors would in a commercial company.
There is also an association secretary responsible amongst other things for administering the membership and the legal side of the association.
The association is totally democratic with minor decisions being made by the elected council and and major decisions being put to a vote of all full members at a general meeting. The association council approve and publish a number of rules which control detail of how the association is run. Details of the legal structures of the association can be found here.