Historically, the United Kingdom has always been putting obstacles when it comes to becoming part of the European Union (EU), since its entry into the EEC in 1973 and after its accession to the EU in 1992 together with Denmark and Ireland. However, they maintained the pound sterling as official currency and decided to stay out of the Schengen area. You have all the information in: «The 'Brexit' in the United Kingdom: meaning, results and consequences«.
You have all the information in: "The 'Brexit' in the United Kingdom: meaning, results and consequences".