No, I doubt any banks would fold - Iran would have it spread over several countries and banks (to decrease their own risk), and I doubt any bank would fold if just one customer wanted its mnoney out. In any case, the latest story I can find on this is a denial:
For the second time in two days, Iran yesterday said it was not withdrawing its foreign currency reserves from European banks, despite reports late last week that it already had begun the process.
"We have not moved or transferred our hard currency assets. The report on the move is not correct," Iran's foreign ministry spokesman Hamid Reza Asefi told reporters in Tehran yesterday.
The Central Bank also issued a statement, declaring there was no wholesale withdrawal of funds from Europe.
"Iran's foreign currency reserves will be kept in all banks we trust in the world, including European and non-European banks," it said.
http://www.gulf-daily-news.com/Story.asp?Article=133328&Sn=BUSI&IssueID=28309Oil isn't used that much for heating in Europe - natural gas has largely taken its place. Oil is still needed for transportation, of course, but it's an international market, and Europe is no more affected than elsewhere by the world oil price.
What may be driving European policy is that European cities would be within range of an Iranian missile long before American ones will be. That would still take years, but they may think that trying to stop it now is easier than later.