Sex work is perfectly legal in the UK, subject to certain restrictive conditions. You cannot work in a "brothel" (i.e. not under the same roof as another sex

Sex work is perfectly legal in the UK, subject to certain restrictive conditions. You cannot work in a "brothel" (i.e. not under the same roof as another sex worker), you cannot have a paid "pimp" (arguably not even to do the accounts or to make sure you are safe), you cannot solicit in a public place. As you say, sometimes police will not enforce these rules, but other times they may use the threat of criminalisation to coerce sex workers. Sex workers typically advocate for the "New Zealand model" of full decriminalisation - which is understood to be safer for sex workers.