Same girl, different names, same agencies different names ?

http://www.yummyasianlondon.co.uk/
http://www.londonladyboys.com/
http://asianplaygirl.co.uk/ts_escorts_london.htm

Looks like many girls are the same, just different name.
I often wonder Are these agencies also the same ? If not what makes them different ? If yes, what's the point. All these different names for the same girls only confuses.

I can't speak on this particular example, but I think it's probably that they're not that good. Bad reviews get out, so they change up their name to stay in business.