UK tourists in the Czech Republic and Switzerland face a race against time to return home before new quarantine measures are imposed.
Passengers are paying hundreds of pounds for seats on flights as people arriving in the UK from those countries after 4am on Saturday will need to self-isolate for 14 days.
Arrivals from Jamaica will also need to enter quarantine, although it is unlikely anyone arranging travel back to the UK after the change in policy was announced on Thursday night will make it in time.
Scotland took Switzerland off its quarantine-exemption list last week.
Swiss International Air Lines is selling seats on a flight from Geneva to Heathrow departing on Friday afternoon for £321, while flights on Saturday – after the new quarantine rules come into force – are available for just £99.
A flight from Zurich on Friday is available for £244.
British Airways put on extra services from the Czech Republic and Switzerland to Heathrow following the quarantine announcement, costing £268 from Prague, £308 from Zurich and £353 from Geneva.
Transport Secretary Grant Shapps warned British holidaymakers that quarantine rules could continue to change rapidly.
He told Sky News: "When people travel at the moment, when coronavirus is still a thing, (they) just need to be aware that unfortunately things can change very quickly and, you know, if you go with your eyes open and you know that things can change, it won't then come as so much as of a surprise."
Reductions in coronavirus cases mean that Cuba has been added to the list of destinations from which people can arrive in England or Wales without entering quarantine, while Wales has also removed the quarantine requirement for arrivals from Singapore.
It came as new enforcement powers entered into force from midnight, meaning that anyone facilitating an unlicensed music event or "any other unlawful gathering of 30 people or more" could face a hefty penalty.
The Home Office has also said that fines for not wearing face coverings where it is mandated – such as on public transport and in supermarkets – will also double for repeat offenders from Friday.
People not wearing masks and those participating in unlawful gatherings can be fined starting at £100, doubling for each repeat offence up to a maximum of £3,200.
In Wales, indoor visits to both adult and children's care homes have been given the green light from Friday.
Visits will be subject to strict controls to help prevent transmission of Covid-19.
Meanwhile, a major media campaign will be launched by the Government next week which will encourage workers to return to the office.
The adverts will promote the Government's aim to reduce the number of employees working from home amid fears that town and city centres are becoming ghost areas as workers stay away.
Labour has criticised the plans as being "unconscionable".
Shadow business minister Lucy Powell said: "It beggars belief that the Government are threatening people like this during a pandemic. Forcing people to choose between their health and their job is unconscionable.
"Number 10 should condemn this briefing and categorically rule out any such campaign."
However, Tory MPs have said that workers need to get back to the office.
Speaking to The Times, Conservative MP Sir Graham Brady, chairman of the 1922 Committee of Tory backbenchers, warned of "devastating consequences" if workers stayed at home.