John Lewis, Currys PC World and toy chain the Entertainer are among retailers that are extending their opening hours to meet a surge in demand ahead of the lockdown in England.
Hair salons are also opening later as all non-essential retailers prepare to shut for a month from Thursday.
It comes amid reports of queues outside stores such as Primark as people rush to do last-minute shopping.
Gary Grant, boss of the Entertainer, said it was "just like Christmas".
His 173 shops are extending their hours until 7pm or 8pm from 5.30pm and expect brisk trading right up until Wednesday night.
"When the closedown announcement was made on Saturday, the penny finally dropped for people that if you take away four of the eight weeks left before Christmas, it is going to make shopping quite hard," he told the BBC.
"Also there is concern toy retailers won't be able to meet the massive increase in online orders because of courier constraints."
Among the retailers changing their opening hours:
- More than a quarter of John Lewis's 42 shops are extending their hours, including in Newcastle, Liverpool, London's Oxford Street and Peterborough.
- Around 200 M&S stores are operating "slightly extended" trading hours.
- Currys PC World is keeping most of its shops in England open until 8pm until Wednesday, with some larger stores open as late as 10pm.
"While we expect footfall to increase between now and Thursday, our extended opening hours will help ease the busy periods in store," said Mark Allsop, chief operating officer at Currys PC World.
Since news of the second lockdown broke on Saturday, there have been queues outside shops in Birmingham, Norwich and Nottingham as people rush to make pre-lockdown purchases.
Shopper numbers were up 9% in the week to Saturday, said data company Springboard, although they remain far below pre-pandemic levels.
"The first national lockdown saw a rise in spending in the days prior," said Kyle Monk, director of insights at the British Retail Consortium.
"We now expect many people to be picking up the items they desperately need before these shops are forced to close by government."
Long queues were seen minutes before a planned 21:00 GMT closing time at Ikea Tottenham in London on Tuesday. A member of staff told the BBC that the store would probably not close until 23:00.
It is not just retailers who are busy. Hairdresser chains such as Regis, Saks and KH Hair Salons are opening earlier and closing later as customers bring forward appointments.
Regis, which owns 56 salons, said it had seen a 30% rise in bookings since Saturday.
Restaurants and pubs are also reported to be seeing a surge in last-minute bookings, as hospitality businesses prepare to shut.
Bookings platform OpenTable said bookings on Sunday were up 11% from a year earlier, following weeks of subdued demand.