A summary of Ethels link:
As said above, prostitution - exchanging participation in sexual activities for money or other goods - has always been legal in the UK. The introduction of the Sexual Offences Act 2003 made some changes.
The laws on working on the street have become 'gender neutral'. Anyone, male or female, on the street (or on a balcony or in a window) can be found guilty of soliciting for the purpose of prostitution.
Anyone kerb-crawling (approaching other people from or near a vehicle they've just got out of for the purpose of prostitution) is particularly at risk, not least as their vehicle can now be seized.
Working alone indoors, or for an agency or in a brothel remains legal, provided the worker is at least 18. Buying sex from them is also legal.
'Pimping', running an agency or brothel is illegal. But controlling another adult's prostitution is now only illegal if you gain from it (or know that someone else does). Looked at another way, gaining from someone else's prostitution is now legal: it's the control for gain that's illegal.