Of course there is no 'exchange rate' between mainland British, Scottish, Northern Ireland, Isle of Man, or Channel Islands currency. If it says "Pound" and has the Queens head on it, then it's valid currency. However... it's rare to have regional banknotes (or coins) circulating so far out from a geographic region, therefore the shopkeeper in Kent may never have seen one before, whereas a Scottish banknote in an area closer to Scotland (like Northumberland) would be much more common and accepted without question. I hear there's 26 million in Northern Ireland banknotes going cheap...

but (I feel) it also insulates the few european "NON EURO" countries
from european (or global) business
as one has to take the risk of changes in (one or more) exchange rates.
(at least for long term conracts)
Business has been conducted with exchange rates (or barter in goods) since time immemorial... there was no problem before the Euro, why suddenly is there a problem with trade between Euro and non-Euro countries now? This is a smokescreen put up by politicians to harmonise Europe into a giant Federal Block to compete with the USA. My boss tells the story of once securing a major contract in Eastern Europe to be told he wasn't going to be paid in any known 'currency' but by way of one and a half trainloads of Titanium instead.

The EC started off as the EEC (note the extra 'E'). European Economic Community (or Common Market as it was also called) whereby trade with our neighbours could be conducted with less bureaucracy and at favourable terms. There is nothing wrong with this, it is after all common sense. However, over time, an 'E' has been lost (or to put it correctly, rubbed-out), it was done quietly and subtly, and most people didn't realise it happened. Suddenly the word 'Economic' no longer existed and a political superstate was born - one which 99% of it's inhabitants neither wanted or voted for it.

Regardless what politicians say, people in Europe are fiercly Nationalistic and proud of it too. You will always hear when asked... "I am Italian" or "I am French" or "I am Dutch", but when did someone ever reply "I am European"? It is not the same if you ask someone from the USA... "I am American" could mean they're from Alabama or Alaska or even Hawaii.

"Vive le difference"