I used two agencies to try and find staff and to be honest, wasn't impressed. They firstly had old contacts, so when I did pick from the profiles they couldn't get hold of them and then because I was just a one salon woman they kept putting finding me someone off in favour of the bigger chain salons. Personally I am of the opinion that every customer should matter, no matter who they are. They were also horrendously expensive and actually I did end up employing one of the girls that the agency had sent me that they apparently couldn't get hold of (via a different route). The best of my staff came looking for me though...
Based on my experience I wouldn't bother with a hair or beauty agency again. Just not worth the waste of time and hassle.