Prime Minister Margaret Thatcher's efforts to soften the ''Iron Lady'' image in the Soviet Union has come up hard against the Kremlin wall. Her foreign secretary, Sir Geoffrey Howe, on a two-day visit to Moscow, found Soviet President Konstantin Chernenko and Foreign Minister Andrei Gromyko in agrim mood, convinced apparently that Britain is little more than a mouthpiece for the Reagan White House.
Paying the first working visit to Moscow by a British foreign secretary in seven years, Sir Geoffrey had hoped to acheive a diplomatic breakthrough for Mrs. Thatcher, and at the same time persuade the Soviets that President Reagan is sincere when he talks about peace.
But back in London after two bruising encounters with Mr. Gromyko and 80 minutes of somber talks with Mr. Chernenko, Sir Geoffrey had the look of a politician who had just barked his shins on a hard object.
Thatcher set out early this year to improve Britian's relations with the Kremlin. She wanted to open up a dialogue with the newly installed Chernenko and was prepared to moderate her previously powerful rhetoric in references to the Soviet Union.
Sir Geoffrey seemed ideally cast in the role of trying to establish common ground with the men in the Kremlin. A soft-spoken lawyer devoid of histrionics, he explained to them that in Thatcher's view, there was no reason why London and Moscow should not have better relations.
As a European, the foreign secretary calculated that he might be more at an advantage in Moscow than an American. In the end, however, he felt it necessary to adopt harsh language to describe the frigid reception awaiting him in the Kremlin.
The Soviets made it clear they were furious with Reagan for, as they see it, trying to turn the US relationship with the Soviet Union into an electoral asset.
Sir Geoffrey also discovered that, in the Kremlin view, Britain was identified with the policies of the Reagan White House. Mr. Gromyko told him that if Thatcher wanted better relations with Moscow, all she had to do was distance herself from Reagan.
For a while Sir Geoffrey listened to Mr. Groymko's criticisms but then his customary patience appeared to snap. Shortly before he was due to meet Chernenko , he went on BBC radio and accused the Soviet Union of being ''illogical'' and ''negative'' in its refusal to talk to the Americans on nuclear arms control.
After his meeting with the Soviet leader, he became even franker. At a press conference, the normally restrained Sir Geoffrey seemed almost to lose his temper.
The Soviets, he said, were not in a mood ''to give peace a chance.'' Chiding Gromyko for not wishing to welcome White House acceptance of a Soviet proposal for talks on space weapons, he declared ''the world cannot afford the politics of the empty chair.''
Reporting to the House of Commons, the foreign secretary said he was disappointed by his visit. Privately he was dismayed by his reception in the Kremlin.