Goblins

Goblins are the acknowledged masters of Great Britain's wizarding economy, in the storage phase and various other aspects. They are known to perform services for a sufficient fee, and will go to war within their clans in order to obtain the right to various contracts. Their major geographic holdings are known to be centered in Gringotts, the massive bank building found in Diagon Alley.
Individual clans are held responsible for specific entities, including the Dumbledore holdings, Slytherin accounts, and Potter deposits. Clans will often challenge each other for the right to administer accounts, and the combat pits are often bloodied when prestigious entities become the center of attention.
The goblins of Great Britain are known to exist in clans, overseen by the Goblin King.