British TV presents Mrs. Thatcher live (almost) from the Falklands

Britain learned at least one lesson from its Falklands campaign last year. There now seems to be no difficulty in sending clear, continuous television pictures across the 8,000 miles separating Port Stanley and London.

A major news media complaint when the war erupted last April was that TV film had to be flown all the way back to Britain, which took several days. No arrangements had been made for satellite transmissions, and suspicions of censorship arose.

But when Prime Minister Margaret Thatcher suddenly arrived in the Falklands for her spectacular visit this month, British viewers were able to follow her progress each night.

True, the films were one day late. But they were flown to Ascension Island, where they were at once sent by satellite to both the BBC and commercial ITV. ITV was even said to have had two camera teams on the bleak, remote islands.

Government officials here acknowledged with a smile that conditions for TV had ''improved.''

But voice contact was sometimes tricky: At one point 10 Downing Street found it hard to determine whether Mrs. Thatcher was wearing a ''dress'' or a ''vest.''

''Given the winds down there, probably both,'' one official sagaciously observed.

Only the BBC had a film crew in the Falklands when Mrs. Thatcher arrived. After some harsh words from ITV, the BBC ultimately gave ITV film of the Thatcher arrival. ITV requests were said to have been supported by 10 Downing Street itself. ITV flew down its own crew, and coverage was extensive thereafter.

Despite criticism from her poliical opponents and from Argentina, the prime minister insisted it would have been ''strange'' had she not visited the scene of so much concern last year. She wanted to thank the people and the troops - and it was clear that the trip was enormously emotional for Mrs. Thatcher personally. She took great heart from it.

To ease the rigors of the 10-hour flight in a spare and spartan Air Force Hercules transport to and from Ascension Island, a trailer was rigged up for Mrs. Thatcher inside the huge aircraft. It allowed her to sit in relative comfort and quiet and to work on the way.