re: Disparate currencies don't benefit any honest person.
Because no-one in the Euro-zone will suffer for what the Greeks have been doing.
Different currencies are essential to allow governments to control things. If you don't control the purse-strings, you control very little and different currencies help insulate the policies of one government from everyone else. Though obviously, this insulation is not complete!
The sensible and economically efficient thing to do is to have a global dictatorship. However, we tend to value self-determination too. Democracy is one way to help government reflect the will of the people and provide self-determination. As democracies get larger however, the value of your vote is proportionally reduced, so while it may still be "democratic" it doesn't allow self-determination because of the push to "harmonise" laws, i.e. differences are erased.
There may be a strong push from business to homogenise people into standardised consumers, but people are different and these differences are often broadly reflected by ethnic and national boundaries. It makes sense to localise financial requirements and planning along these boundaries as well.
This isn't an EU-only issue. While we may decry censorship, Google's declaration that it will try to leverage international treaties to override national sovereignty is equally disturbing, regardless of the good outcome.
I'm not even sure why the newspaper article has come out now. I haven't checked recently, but from a balance of payments viewpoint we probably need to export more. The massive drop in value of Sterling will have provided an enormous boost to exporters and discourages imports.
That wouldn't be possible if we were inside the Eurozone.