Not so. The girl is breaking the law, but a client is not, unless he solicits a woman for the purposes of prostitution; she breaks the law by soliciting him - unless, as l said earlier, he propositions her ( or (quite literally) curb crawls) he commits no offence.
Street Prostitution and Kerb Crawling - InBrief.co.uk
External Link/Members Only
Your link doesn't work, the relevant part is posted below.
External Link/Members OnlyKerb crawling
It is illegal for a person to solicit prostitutes from a motor vehicle while on a street or public place under Section 1 of the Sexual Offences Act 1985. Kerb crawling is an indictable offence under section 71 of the Criminal Justice and Police Act 2001 if it causes annoyance or disturbances to people in the neighbourhood or if it is persistent behaviour.
Kerb crawlers can be penalised with a maximum fine of £1000 and, under Section 1 of the Powers of the Criminal Courts Act 2000, they can be disqualified from driving.
Other measures that can be used to combat kerb crawling include issuing anti-social behaviour orders (ASBOs) after a person is convicted of kerb crawling, civil injunctions and acceptable behaviour contracts in which kerb crawlers agree to change their behaviour. Local media may be encouraged to name and shame those who are convicted of kerb crawling.
How do you get to pick her up without stopping and asking,

as soon as you do you break the law. Even driving slowly through a known area can get you a tug from the law.
If you still think it's legal and or worth the risk crack on.

Edit
An update from the CPS website. -
“Kerb Crawling”Relevant Law
Section 51A of the Sexual Offences Act 2003 (as amended by Section 19 of the Policing and Crime Act 2009) creates a summary-only offence for a person in a street or public place to solicit another for the purpose of obtaining a sexual service. The reference to a person in a street or public place includes a person in a motor vehicle in a street or public place.
This replaces the offences of kerb crawling and persistent soliciting under Sections 1 and 2 of the Sexual Offences Act 1985. The amendment removes the requirement to prove persistence. This enables an offender to be prosecuted on the first occasion they are found to be soliciting, without the need to prove persistent behaviour, or that the behaviour was likely to cause annoyance or nuisance to others.