If it were not for the Iron Curtain, for sure Bulgarians and Romanians, but also Slovaks, Czechs, Poles and all the others for whom the Berlin Wall was an obstacle in front of their economic and individual freedom, would not have been the poor relatives who endanger the wellbeing of their western cousins with their desire for better life, better pay and more possibilities for work. If the Iron Curtain never existed, most probably a Eastern European would not have been a synonym of poor, corrupt, but in most cases well educated person.
The European West has managed to swallow eight eastern European states and most of all the Polish plumber, but choked with the Bulgarian and Romanian low-qualified workers and especially the Roma, who are now free to work and live everywhere in the EU as of January 1st.
The problem is though, that the concerns of a Bulgarian-Romanian invasion are not only British. There are worries in The Netherlands, too, which has often played lately in the anti-integrationist choir with the United Kingdom.
Source (English language): http://www.euinside.eu/en/news/netherlands-seeking-a-solution-to-bulgarian-romanian-migration