Correct me if i'm wrong but didn't they default in 2012?
Devaluing their currency has proven to be a failure in the past, once again, why would it be different this time?Devaluation of a currency is better than remaining inside a currency zone of which you are not suited to. If you devalue, your at least bringing your currency into line with your economy where as at the moment Greece is completely unsuited to the high price of the Euro in terms of its economy.
Britain, at the end of the imperial age, famously devalued under the Wilson Government when our economy was in clear decline and we'd lost the colonies: the Pound Sterling wasn't worth what it was and was only being shored up by HM Treasury backing it with assets... a temporary fix.