“Étude” is a term specific to the French market: an “étude” is an auctioneer's office that conducts judicial auctions.
Voluntary auctioneers (as opposed to judicial auctioneers) are referred to as “Maisons de ventes” or “Hôtel des ventes”, or even “Société de Ventes Volontaires” (SVV), depending on the type of structure, but all of them are auction houses.
Please note: The term “auctioneer” is a commonly used term. For more information on this terminology, see this article.