BERLIN—A growing list of European Union nations moved to ban flights from the UK on Sunday and others were considering similar action, in a bid to block a new strain of coronavirus sweeping across southern England from spreading to the continent. France, Germany, Italy, the Netherlands, Belgium, Austria, Ireland, and Bulgaria all announced restrictions on UK travel, hours after British Prime Minister Boris Johnson announced that Christmas shopping and gatherings in southern England must be canceled because of rapidly spreading infections blamed on the new coronavirus variant. Johnson immediately put those regions into a strict new Tier 4 restriction level, upending Christmas plans for millions. France banned all travel from the UK for 48 hours from midnight Sunday, the prime minister’s office announced. The French statement said that would buy authorities time to find a “common doctrine” on how to deal with the threat. It specified that “flows of people …