On a more sensible note, just try it. Go in, pay your cash, lay face down and see what happens. We've all walked away with blue balls from "legit only" Chinese, Thai and indie providers, but the only way intelligence within the community grows is by blokes taking the 'nothing ventured, nothing gained' approach. Like me and the rubbish experience I had in South London in 2016 (December, it was Christmas and I was pissed).
We know that such UTR places exist as propaganda by anti-prostitution lobbies refers to them (so-called black market of spas and salons, including nail salons!) but we'll never find out unless we're Dora the Explorer ourselves (the next time I spot one, I will TOFTT).