Not as odd as the Indian district of Dahala Khagrabari. It's surrounded by part of Bangladesh, which is surrounded by part of India, which is surrounded by Bangladesh
England is a country (afaik). Enclosed within a nation-state called the United Kingdom. Great Britain is not the same thing. The UK is made up of England Scotland Wales and Northern Ireland, while Great Britain is the same thing plus all the other fiddly bits like the channel islands and the Isle of Man. The government in London has authority over the UK, but not over the channel islands nor the Isle of Man. This distinction is most obvious in regards to the EU. The Isle of Man is not part of the EU, nor are the channel islands. The governments of the channel islands are sort of residual fuedal. For most Brits Great Britain = UK, but that is not the case. Certainly not legally. Birching (that is flogging with a flexible branch cut from a birch tree) was legal in the Isle of Man until the early seventies, I think. But it most certainly was not legal in the UK. The Queen is the head of state of the whole lot regardless of the form of government used.