"there is such thing as voluntary trafficking"
There isn't. The legal definition of trafficking has nothing to do with crossing borders or travelling a long distance- it's about being forced/coerced.
Correct. There is no such thing as voluntary trafficking. The prostitutes you are thinking of, who travel to this country 'voluntarily' to be prostitutes, are included under the 17,000 figure in my last post.
I'm not sure Katiesmummy understands what trafficking is or what happens to women trafficked for sex. Did you read the article I linked to? The prostitutes that are trafficked have their passports removed, are locked in a room and violently assaulted and raped. Threats are made to family back home to make sure they behave and they don't earn any money. It's all taken by the traffickers.
Prostitution is gradually becoming more and more normalised in society and that's why your "d"h felt he was entitled to go and pay one for sex. Consider the effect of Trading Places, Pretty Woman and Belle de Jour/Secret Diary of a Call Girl - all very empowering aren't they? But don't be fooled into thinking they're all like Belle de Jour or the prostitute that your h visited.
Sex traffickers want prostitution to be both normalised and acceptable in society- they tend to travel to countries where there are punters ready and willing to part with their money with few questions asked because that's they way they make their money easily. When an activity is legal it is normalised and acceptable.
And, sex tourism is far more prevalent in the Netherlands and the Amsterdam red light district, where prostitution is is legal, than in Sweden, where the purchase of sex is illegal. No one could dispute that.