Why the UK is not Greece 

Gordon Brown, the current prime minister in the UK was staunchly against adopting the euro when he served as chancellor of the exchequer. He designed 5 economic tests that the UK would have to pass to even think about adopting the euro. These conditions were, of course, in addition to the Maastricht Criteria, which were the EU's conditions for countries to join the euro. As a result the UK never joined.

This decision seems like a brilliant move now (although its unlikely to help Brown win his upcoming election). The Financial Times  has a great summary of how the ability to depreciate its currency has helped the UK maintain its economic footing. Neil Hume adds his thoughts here, Paul Krugman adds his thoughts here. 

Of course whenever economists start arguing why a country is NOT going to be hit by contagion, you have to think about why they were contemplating the issue in the first place…