People migrate all the time...
Since the EU was formed, it is easier to migrate between countries.
Within the EU migrants may come:
In 2004, Poland and seven other Eastern European countries joined the EU. This increased migration into the UK. The largest group of migrants were from Poland.
Immigrants after the world wars mainly came from Commonwealth countries. Immigration was encouraged by the government. Many immigrants provided labour for textile factories, transport, health or steelworks. The UK tightened migration controls in the 1970s.
There are sometimes patterns of migration globally as the map below shows.
Worldwide migration trends 1918-1919