HI!
I am a Counter Manager for Benefit. I don't know how different the line is in London, though I know it is very very popular there, but everything the above poster said is true. I love working there, as I really like the cosmetics, and the fun, be yourself atmosphere, but it is a lot of pressure to meet sales goals, and at least here, the brand is kind of unknown in my area so it is not only trying to get people to sit down, but trying to get people into a brand they don't know.
I used to work for MAC, and while they are totally different, there are pros and cons to both. At MAC, you don't really have to "traffic stop" as the store is always packed, but it is crazy and much faster paced. At Benefit, you really need to go find your customers, and sometimes I really do feel like I am bothering people. I like it for now, because I need a job and I like the people I work with but it wont be forever. I would much rather work at a more recognized brand.