I'm personally interested because I used to live in Birmingham, and the plethora of bordellos masquerading as massage parlours was a very poorly kept secret. In fact, a quick web search yields evidence (text only, but may not be safe for your work) that the parlour in question appears to have been operating as a house of ill repute since at least 1995. West Midlands Police have not enjoyed the best of reputations in the past, but they surely could not have been unaware of the true nature of these businesses. Instead of turning a blind eye, would openly legalised and regulated prostitution help to prevent the type of abuse alleged in Birmingham? And perhaps a more relaxed approach to immigration would pull the carpet from under the feet of people traffickers. However, is it just out of the frying pan, into the fire for them? Even once such women are freed, they are still illegal immigrants in the eyes of the law and can expect detention and repatriation. The European Convention on Action Against Trafficking in Human Beings would allow them temporary residence and state support, but the UK has not signed up to it. There are, however, others who are willing to help. Anecdote: several years ago, one of my friends in Birmingham had his girlfriend over for the weekend, and she wanted to get a massage. He called around several "massage parlours" advertised in the phone book without success; one of them said, "Well, I suppose one of the girls could do that..."
White slavery in the UK Police in Birmingham, UK, are reported to have rescued nineteen women from ten countries from white slavery. (The term is archaic; the practice, sadly, isn't.) They were allegedly being locked in the establishment at night, and kept in by day with the assistance of an electric fence around the back garden.