London — * The sign in the supermarket in Chertsey, Surrey, reads: ''We do not sell Argentine corned beef.'' Plastic packets of sliced beef have been removed from the shelves, and the only cans in sight wear labels reading ''Made in Brazil.''
* The British government has withdrawn all maps of the war zone from the country's largest map dealer because of a sudden shortage in official circles.
* Jut-jawed retired admirals and admirals fill the television screens every night, discussing strategic moves, flank attacks, close-in support, firepower, ranges, and morale.
All of it adds up to a country at war.
Prime Minister Margaret Thatcher told Parliament May 27 that British troops at Port San Carlos had begun advancing.
Britain is adapting rapidly to a situation completely new to anyone under 45 or 50 years old here. And the conflict keeps on reaching into more areas of daily life.
''Every morning I wake up and turn on the news, hoping that the fighting has stopped and that no one else will be killed,'' one man in London said the other say. ''It's like a nightmare.''
No sooner have correspondents filed their latest dispatches about the latest bombing raids and shelling attacks than they race back to their desks and file more on new information that keeps coming in.
The naval ports of Plymouth, Portsmouth, and Gosport mourn for the sailors killed on the five British ships lost to date, and the Defense Ministry has set up a South Atlantic fund to which members of the public can contribute donations for the families of those killed and wounded.
Anguished wives are asking their members of Parliament why news of ship losses cannot be held until all next of kin have been informed. Families say that they have spent sleepless nights after hearing that ships have been lost. They have waited for official phone calls or visits throughout the night and the next day, not knowing if their own relatives have been killed.
At first, when Argentine threats to the Falklands rated only a few paragraphs on the back pages, the Falkland Islands were a mystery: ''I thought they were in Scotland,'' one woman in my local village in Surrey was to say later.
When the blue and white Argentine flag was raised after a landing on South Georgia, the dispute seemed faintly comic. Lord Carrington, the foreign secretary, was preoccupied with the European Community and with a visit to Israel at the end of March.
On April 2 Argentine forces invaded the Falklands and the war mood slowly but surely began to build here. Life was not to be the same again for a long time.
To begin with, it seemed unreal: a gigantic task force assembled in 48 hours, flags fluttering as big ships steamed off to who knew what at the other end of the world.
So Britain seemed to be talking of nothing else. ''The Falklands'' became an issue of national unity and will. Prime Minister Margaret Thatcher took charge, refusing to countenance the concept of defeat.
The Ministry of Defense failed to make proper provision for reporters or for sending back television or still film. News programs and newspapers turned to retired admirals and generals for war comment and predictions.
British reporters complained more and more loudly that the ministry released information selectively and often after facts had come from Washington or Buenos Aires. Reporters were totally dependent on ministry briefings and complained that on one occasion they had been given false information in an effort to mislead the Argentines. They felt that if they complained they might be excluded from the briefings.
Over my back fence I listened to neighbors solemnly saying: ''We British are funny - when someone tries to push us around, we stand up to them. No dictator is going to tell us to get off those islands.''
No one in my Surrey village wanted war but most people, reflecting the national opinion polls, felt that once the task force had been sent, it must logically be used if diplomacy failed.
To the close observer, Britain seemed to develop a kind of split personality.
The initial House of Commons debate April 3 was bellicose and jingoistic, but as the mood settled into sobriety and concern, the right-wing popular press on Fleet Street, much of it owned by Australian Rupert Murdoch, kept up a frenzied drumbeat of warlike headlines. Many people thought it grossly simplistic and overdone.
In fact, radio phone-in programs and public opinion polls made for the Economist weekly and commercial and BBC television, indicated a steadier public mood underneath the shouting.
Some families of the men being killed in action bitterly attacked the BBC's effort to be impartial and tell both sides of the story, and Mrs. Thatcher herself weighed in with sharp criticism. The BBC admitted some errors, and even the anchorman of the weekly BBC ''Panorama'' program, Robert Kee, resigned with a blast of criticism.
Now the criticism has died down.
As the month of May ended, the mood remained resolute in Britain - as long as British losses remained manageable - but the loss of a big ship or many more men could put Mrs. Thatcher under more pressure.