If an escort displays a face pic on their AW profile and has feedback, then you'd have to assume that they pay tax. So I think more are registered than many here give credit for.
I disagree you would have to assume they pay tax. Some for example will work for a pimp who wouldnt be worrying about such a thing, some other WGs are as thick as two short planks and wouldnt even consider such a thing i would imagine.
What i do think is the inland revenue would use any evidence they find on A/W etc to help with their case against a non tax payer to assess how long they hadnt been paying tax for, perhaps after getting a tip off.
GP Parties who got done a couple of years ago had their reviews on auto-censored virtually immediately taken down from public view following their raid and arrest, i assume this was to try to hide info from the police, tax, benefits and POCA. It may well of helped as the owners POCA judgement was under £100,000 yet he had been operating for 7-8 years or so and in that time must of taken well over a million pounds. He probably blew most of his profits though, he was as thick as pig shit.