Those who do not return to the country by 4 a.m. on Saturday will need to be quarantined at home for 14 days, which means they cannot work or shop.
But according to reports, they were told they could stop at the supermarket on the way home to pick up food and supplies, The Mirror reports.
A government source told the Telegraph that people were allowed to go to the supermarket on their way home from the airport, train station or ferry port.
They stressed that this trip was only a last resort, however.
According to official guidelines, people should only leave their homes for basic necessities such as food and medicine in exceptional circumstances where delivery is not possible.
Brits in isolation are not even allowed to walk their dogs and if they do, they face a fine of £ 1,000.