Not directly saying trafficking but if you know the Chinese and Thai scenes (and I think you guys do), you'll know that girls do sign up to go on tour - some re-paying their transport here, some are resident but need the money. Different reasons for doing it. I know girls who have hopped on that wagon, when it suited them. Some do the FS for a while and then go back to fbsm. The Thais stay separate from this Chinese scene but they do sign up, through 'agents' and move around, too.
I gave up on that scene quite a few years back, having had excellent to worrying punts and everything in between. I've been to the original houses, at Ealing and South Harrow and subsequent flats at Golders Green, Hammersmith, West Ealing and around NW London. The scenario doesn't seem to have changed much and I'm going back to this site's forerunner, for where it was first highlighted. They were more blatantly advertising Full Service but over the years, slipped into fbsm too. I still read the sites like Craigslist, Vivastreet, Backpage and the rest - and here, of course - so see that not much has changed, except the rise of the TCM scene. That's given the 'more independent' Chinese girls a bit more choice in where they work. Also, there's more money, for them, in the TCM scene than there used to be.
The common factor is the Chinese minder. Always perfectly pleasant guys, by the way - wouldn't cross them, though.