Euro Crisis, Can Cameron handle it?

I have been watching David Cameron over the last week or so and have noticed a steady increase in him dictating to the countries in the Eurozone and more specifically, Greece. His tone is changing by the minute. It seems to me that the nearer Greece comes to leaving the Euro, the more he seems to panic. My question to him would be, "is there something you are not telling us David?" He has said all along that we in the UK are prepared for the possibility of Greece leaving, but, and this is a big but, he has never come out and said exactly how a Greek exit would affect us. He and his government, along with the Bank of England have a plan, they say, but, they will not divulge anything about the so called plan to us. No one in this country has mentioned the dreaded "run on the banks" but I would bet that there would actually be a run on the banks if Greeks withdrew. The only question is, how big a run would it be? In Greece, bank holidays and closing ATMs have been mentioned along with a military presence on the streets. Could it happen here in the UK? I wouldn't bet against it.
Interesting but scary times ahead.