"working as a prostitute in private is not an offence, and neither is working as an outcall escort." (http://en.wikipedia.org/wiki/Prostitution_in_the_United_Kingdom#Current_laws)
...this is currently true. For now. There is a move to make it illegal to pay for sex.
I do not currently live in the UK, but I have very strong feelings about this partially because I'm a caring human being and smart enough to know that this is a devastating move towards making people's lives less safe, and partially because I have history with legal and illegal sex work and it scares me that so few people seem to realize the reality of the hell a person can go through because of the legality of sex work, and the danger element that making it illegal adds to sex work.