Anglais:immigration,racism and violence in the UK

C'est le thème de mon devoir.
question 1:what are the different sources of immigration in the UK?
My answer without correction
The UK was the most important empire in the 19th century.The UK,nowadays,is composed of fours nations in one with England,Wales,,Scotland and Nothern Ireland.But,formerly, the UK was composed again of colonies like the Caribbean,the East Africa and West Africa,India,a part of China and other South East Asian countries.So the UK became a multi-cultural and a multi-ethnic society.Moreover many people came from former colonies in particular immigrants from British Commonwealth countries.At the end of the 50's the UK needed more people to fill largelly unskilled job.Besides,many europeans from Eastern and central Europe, includind Jews escaping Nazism and communist regimes.

N'hésitez pas à faire des corrections(syntaxe et civilisation).