"Thousands of Greeks" is a sort of alarmist quote from here:
http://www.theguardian.com/uk/2012/jul/03/david-cameron-immigration-greece-uk
"The worst-case scenario is understood to cover a Greek exit from the euro, which could trigger a near-collapse of the Greek economy and the flight of hundreds of thousands of its citizens who are currently entitled to settle in any EU country.
The prime minister said Britain is prepared to take measures to avoid a major influx of Greek citizens. "I would be prepared to do whatever it takes to keep our country safe, to keep our banking system strong, to keep our economy robust. At the end of the day, as prime minister, that is your first and foremost duty.""