Soviet President Mikhail S. Gorbachev ended a whirlwind visit to Britain Friday with one of his by-now-almost-patented unilateral disarmament gestures and a fresh warning to Western politicians that it is time for them to respond more positively to his "new thinking."

The gesture - a halt in production of nuclear weapons-grade uranium and the closing by 1991 of two reactors used to make weapons-grade plutonium - was quickly dismissed by independent experts and the Bush administration as relatively meaningless in military terms.But his warning that a NATO plan to modernize its short-range nuclear arsenal could force the Soviet Union to follow suit and jeopardize conventional arms-reduction negotiations in central Europe is considered likely to put further strain on a Western alliance already at odds over the modernization issue.

Gorbachev's moves came amid a dazzling display of traditional British pomp and circumstance that culminated with lunch at Windsor Palace, where Queen Elizabeth II accepted the Soviet leader's invitation to visit Moscow at an undetermined future date.

The monarch's acceptance, which required the approval of Prime Minister Margaret Thatcher's government, underlined the extraordinary warmth that has come to coexist with continued, sharp policy differences in the complex Soviet-British relationship.

A visit to Moscow by the queen, the first since her distant relatives of the Russian royal family were overthrown in the 1917 Russian Revolution, would represent a highly symbolic endorsement by Britain of the changes that Gorbachev has wrought in the Soviet system. At the same time, Thatcher's government hopes that the prospect of the visit will become another incentive for the transformation to continue.

Earlier Friday, Gorbachev assured several hundred invited dignitaries at Guildhall, the ornate and historic seat of the city of London's government, that "there is no turning back" from his program of reform, known in Russian as peristroika. And he hailed Britain as "the nation whose political experience has enriched the history of the world."

For all the superlatives, however, Gorbachev's Guildhall speech was a disappointment to those who had expected him to announce some major new arms control initiative or to expound his vision of a future "common European home" for the peoples of East and West.

Instead, he stressed what he described as the bankruptcy of the Cold War "philosophy of confrontation" and called for a new era of "international interaction" that will be necessary to solve the "various dangerous and pressing problems facing mankind."

President George Bush, asked at a press conference about Gorbachev's announcement, said that he had not seen it. But he rejected Gorbachev's criticism of the day before that the United States is dragging its feet rather than moving forward with the Russians on arms control and that the Bush administration is taking too long reviewing foreign policy.