Nobody I know wants United States of Europe. The European Union is completely undemocratic at it's core, our national leaders have made sure that the electorate has minimal powers and influence over their supranational policing. Sovereignty of the people conflicts with the sovereignty of nations.
I think the only viable EU is a United States of Europe, in which the current countries disappear, and you only have a Federal state and what is currently regions in the current countries.
Whether a EU is desirable for the UK is another debate. The UK is one of the rare capitalist countries in Europe while pretty much all the other countries are social-democrat if not outright socialist countries, with the high unemployment and low growth associated.