Why the UK won't join the Euro
1) The Pound Sterling is still a very strong currency and widely used as a medium of exchange in international trade
2) Like it was stated. To convert to the Euro requires you to give up 'local' policing of economic matters. While in the long run, a centralized government for all of Europe will be good, in the short run it causes economic turbulence and since most people look short term, this is what they see
3) The English, like everyone else, are very nationalistic. The idea of giving control of their currency over to say the Germans or French is not a pleasant one.
IMHO I don't think the UK will join the Euro until one of two things happen. The Euro gains ground and stabalizes against the dollar, or the pound loses ground against either the Euro or dollar. Otherwise it would be unwise to give up such a strong currency in favor of a relatively weaker one.
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Ever wonder if illiterate people get the full effect from alphabet soup?