I've always just assumed that(given geographic spread of the usual hauns, esp belfast) that if the joints aren't being run by paramilitaries, then they're as a minimum stumping up protection money. There's no way in hell cash operation massage joints etc are operating out of lower Ravenhill, the Village, N'Ards road etc in residential areas under their radar. Same in Portadown etc. More than once I've knocked an appt on the head due to "interesting" characters loitering in doorways a few doors up. Burner phone or no, we're only a photo away from an extortion racket.
Just another reason to keep your ££ in your pocket and save for a weekend across the water.