Agencies for TV/cinema commercials??

[cully]

Does anybody have a list of agencies who provide actors/models for TV/cinema commercials? I'm thinking of organizations like Crawfords which has an A-Z of actors/actresses with picture which might prove invaluable to people like us who are constantly trying to find out who relatively obscure performers are when we see them in ads. I had just about given up on finding out who the girl was in the Danone Bio Activia ad when I spotted her (Joanne Heywood) in the extensive Crawfords A-Z!