First, some numbers. Scotland has a population of 5 million; Wales: 3 million; Northern Ireland: 1.75 Million; (in total less than the population of London).
England: 51 million.
Many of the British citizens of Scotland, Ireland and Wales claim they want independence from England and regularly deride their English 'masters'. Their independence would be economically very beneficial to England. Most English people are in favour of Scottish and Welsh independence, and the reunification of Ireland, largely because of their regular whinging, sniping and drain on funds. The only people who seem interested in maintaining the Union are those with a vested interest; eg avid Royalists and politicians; and those Welsh, Northern Irish and Scots smart enough to realise that they couldn't survive without England.