The intermediary here is mostly notional. CEA is the only entity with legal existence, but on a practical level nearly all employees are effectively GWWC, 80k employees etc., with the CEA employees mainly being for shared services such as operations. So there isn't really much of overhead or anything.
Both GiveWell and the Centre for Effective Altruism (CEA) --an Oxford-based umbrella organization consisting of Giving What We Can, 80,000 Hours, The Life You Can Save, and Effective Animal Activism-- have been discussed here before. So I thought some folks might want to know that these organizations are recruiting for a number of positions. Here are relevant excerpts from the official job announcements:
(Full disclosure: I'm friends with the co-founders of CEA and have donated to Effective Animal Activism.)