Thousands of lorry drivers spent Christmas Day in their cabs in Kent waiting to cross the English Channel.
Other countries have also reported cases of the new variant: on Friday, Japan confirmed five infections in passengers who had all arrived from the UK, while cases in Denmark, Germany, the Netherlands and Australia were reported earlier.
Last week, France lifted its national lockdown, but the government said the infection rate had not fallen sufficiently for a further easing.
France has reported more than 2.5 million confirmed Covid infections since the start of the outbreak, with more than 62,000 deaths - the seventh highest total deaths in the world.
The country's first batch of Pfizer-BioNTech vaccinations meanwhile were delivered from Belgium to the health system's central pharmacy just outside Paris on Saturday, AFP news agency reports.
The first shots are due to be administered to patients at two facilities for the elderly - in Sevran and Dijon - on Sunday.
What is the new variant?
The new variant first detected in southern England in September is blamed for sharp rises in levels of positive tests in recent weeks in London, south-east England and the east of England
About two-thirds of people testing positive in these areas could have the new variant - but this is only an estimate, the Office for National Statistics (ONS) says.
Three things are coming together that mean the new variant is attracting attention:
It is rapidly replacing other versions of the virus
It has mutations that affect part of the virus likely to be important
Some of those mutations have already been shown in the lab to increase the ability of the virus to infect cells
All of these build a case for a virus that can spread more easily, says the BBC's health and science correspondent, James Gallagher.
However, there is no evidence that the new variant is more lethal, and the leading vaccines developed in recent months should still work, experts say.