This movie is one that starts slow, continues slow but builds like a kettle that's been put on to boil.
There's a few plot holes that could easily have been plugged with another 5 or 10 minutes of screen time but if you ignore them and stick with the primary focus of the movie, you can get over them easily.
This movie was a little gentler in dealing with a very large problem, the trafficking of women for sex and money. A much grittier and more compelling tale would be the movie "The Whistleblower" which details the practise by telling the true story of the involvement of the U.N and large global corporations.
All in all, give this movie a watch because it does an excellent job of showing a little of the underworld that exists in London.
No spoilers this time, just watch and ...I won't say enjoy because it will leave you thinking at the end, so, just experience.