There are massive problems with the European Union as a concept.
Free movement of goods and workers (the beginning of the EU) was a great concept, and still is. The idea being that workers and goods can go where economic growth is. It is how I came to the UK in the 90s, I had a skill that was in short supply in the UK so I got a job here with no paperwork or red tape to be gotten through. When the economy and my job area changed, I moved to another country.
Free movement of goods and workers is a good thing, and I don't think people in the UK have a problem with immigrants who come here to work.
A massive problem with the EU is that it is NOT democratic. The laws are created by the European Council (members are appointed, not democratically elected!) and the European parliament only has an advisory role.
If there is a clash with a national (say british) law and a European law, the European law takes precedence.
Essentially, the more involved in Europe a country is, the more autonomy and democracy it loses.
You will be ruled by fat cat bureaucrats, who cannot be voted out, as you never even voted them in.
I think the fact that so many British people resist this idea strongly is great, as the EU is far from perfect.
Even as an immigrant I can see that Farage has some valid points, and politicians need to explain the whole EU thing to the public (essentially, we give up autonomy and gain, possibly, economic growth and stability. Thought the last argument is hard to press home after Greece and Spain disasters...)