However, I am not sure that joining the Eurozone would act as a panacea. Greece fudged its data to join and did nothing to bring their finance in order. Neither has Portugal. It’s all about internal discipline. Spain's growth was more about being credit driven (via the housing market route) and there was nothing much fundamental about it. Unemployment at 25% is the result as the bubble pricked.
Fact is, if one looks at the history, things are not very encouraging. The biggest proponents of the Stability & Growth Pact (SGP) viz France & Germany continued to flout 3% deficit cap with impunity. Yet, the Council of Ministers failed to apply sanctions against them although punitive proceedings were started when dealing with Portugal (2002) and Greece (2005), though fines were never applied. The reasons that larger countries have not been punished include their influence and large number of votes on the Council of Ministers, which must approve sanctions. It is unlikely UK would have been much different. Agreed, UK needs to do mend its ways. But it is also important to realise that the extent of deficit reduction Greece and Ireland needs to do would, in all likelihood, plunge these economies into recession. A big economy like UK plunging into recession has its own implication.
Actually there’s no right or wrong action. There are both pros and cons of being part of the Eurozone. A bigger question though is can UK afford not to have an independent monetary and fiscal policy? In this regard, Krugman’s views (link pasted below) does sound logical. (http://www.nytimes.com/2010/02/15/opinion/15krugman.html?em)