England. For those confused as to why some British people refuse to consider themselves European despite obvious similarities (genetics, language, geography, culture, EU, etc) it's because in some respects the UK is distinctly different from the rest of Europe and much more so than most 'other' European countries are from each other. These include but are not limited to a different political system (two party first past the post vs multi-party proportional representation), legal system (common law vs civic law) and immigration system (border controls vs citizen card internal controls). On top of that the UK has historically been more focussed, or at least successful, internationally than in Europe so shares those differences from Europe with many international countries. When European countries create EU legislation they tend to do so without consideration or perhaps recognition of these differences therefore increasing the barrier of entry for Britain. Whereas it may be a logical continuation for continental countries, in many cases it requires a large overhaul in the UK. Combine that with the fact that Britain has historically been more successful than most if not all European countries with good reason to believe its ways are as good if not better than the ones continentals use and you can understand the opposition.