paying for sex is currently illegal in the UK
I understand from the below link that:
In England, Wales and Scotland, the exchange of sexual services for money is legal, but a number of related activities, including soliciting in a public place, kerb crawling, owning or managing a brothel, pimping and pandering, are crimes. Although the legal age of consent is 16, it is illegal to buy sex from a person younger than 18. In England and Wales, it is an offence to pay for sex with a prostitute who has been subjected to force even if the client did not know.
https://en.wikipedia.org/wiki/Prostitution_in_the_United_Kingdom