The approach to identifying practical problems is in the interaction between the United Kingdom (UK) and the European Union (EU), the consequences of the UK's withdrawal from the EU, and ways to overcome them by coordinating national institutes' activities in the UK and the EU. The specific research results that characterize the novelty of the study are as follows: it was found that the UK's withdrawal from the EU is a specific form of manifestation of the global tendency to revive elements of isolationism in international economic relations; it was found that the work of the European Commission and the UK government on further cooperation between the EU and the UK can be used to create models of cooperation between the Eastern Partnership countries and the EU in the future. The aim is to study the theoretical and practical foundations of the European integration of the UK in retrospective and modern times to identify problems of cooperation with the EU, a general analysis of the causes and possible consequences of leaving the EU, prospects for further development.