A 1998 report funded by the Swedish government documents women voluntarily coming to Western European destinations from eastern and (mostly) central Europe and indeed from eastern to central Europe, for the purposes of prostitution. Finland and Norway report "busloads" of Russian women coming on short holiday visas, and even for weekends, to earn extra money in more profitable western markets.Whilst detailed studies are lacking in most countires, Kelly & Regan report (.pdf) women from numerous countries in central and eastern Europe, Asia south America and Africa working in prostitution in the UK, whilst confirmed trafficking cases have involved victims from Thailand, Albania, Brazil, Czech Republic, Hungary, Lithuania, Portugal, Spain, Romania, Slovenia and the Ukraine. 

The tables below document the proportion of migrant prostitutes in the various Western European countries, and their countries of origin.  The data is from EUROPAP Regional Reports, compiled for the purposes of this website.

The top table shows that in some countries substantial numbers of foreign sex workers originate from another EU country.  A country not mentioned in the source document is Luxembourg, where foreign workers make up almost 100% of prostitutes.  In a country like Luxembourg or Belgium the proportion of foreign workers from other European countries is so high that their numbers will increase when a neighboring state has a 'crack down'.