No, it is not right - I have no idea what this site is or where they've got their information from (I suspect it's the US) but talking about selling, offering to sell or selling sex in the UK is perfectly legal and always has been. As is buying it.
The only offence even vaguely relating to this is soliciting, which only concerns public places and is a public order offence along with others which cause a public nuisance. Even then the exchange of money for sex is not illegal, it's loitering or approaching somebody with the intention of doing so that is.
There is no such thing as the UK National Escort Association in any credible, official sense and this reeks of a new tack by the scammers, to me at least. I wonder at what point they'll start asking people for money for something?
EDIT: Having just skimmed the content of this site, I can categorically say that it is possibly the biggest pile of steaming horseshit I have encountered in an extremely long time. It is clearly cut and pasted from something Stateside (much of the spelling is American) and the 'advice' is so bad it's almost funny if there wasn't a slim chance that somebody might believe it. They're actually recommending people use Paypal, ffs
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