"Illegal drugs and prostitution boosted the economy by £9.7bn – equal to 0.7% of gross domestic product – in 2009, according to the ONS's first official estimate."

"A breakdown of the data shows sex work generated £5.3bn for the economy that year, with another £4.4bn lift from a combination of cannabis, heroin, powder cocaine, crack cocaine, ecstasy and amphetamines."

"According to the estimates there were 60,879 prostitutes in the UK in 2009, who had an average of 25 clients per week – each paying on average £67.16 per visit"

http://www.theguardian.com/society/2014/may/29/drugs-prostitution-uk-national-accounts