Zimbabwean opposition leader Joshua Nkomo arrived here this morning saying he has no desire to become a permanent exile and will return home if he gets personal assurances from officials there that his life will not be endangered.

Nkomo, who fled to Botswana last Tuesday, was met at Heathrow Airport by British security police and immigration officers. After a brief conversation, they gave him permission to remain in Britain for a week.

"I don't know how long I will be here," Nkomo later said at a press conference, "but I have no intention of settling anywhere but Zimbabwe."

A senior Zimbabwean government official, Information Minister Nathan Shamuyarira, followed Nkomo into London several hours later and urged that he return, asserting that he will be "safe and free if he returns. Not only will he be protected, but he will have an opportunity of talking to the leaders." The minister, however, said he had no plans himself to meet Nkomo.

Nkomo, 65, one of the founding fathers of Zimbabwean nationalism, sought sanctuary in Britain for several years in the 1960s before returning to southern Africa to join the civil war against the white-led Rhodesian government. Since the former colony gained independence in 1980, Nkomo has gradually fallen out with the country's other main political figure and his wartime ally, Prime Minister Robert Mugabe.

"I left home last week in very unbecoming circumstances," Nkomo said of the decision to abandon his house and family in Bulawayo after government troops raided the premises, shooting his driver and another man. "It was then that I realized my life was in danger," Nkomo added. "I could not do much in my grave."

In Harare, Nkomo's wife said today that she tried to leave Zimbabwe shortly after her husband because she, too, feared for her life. Johanna Nkomo, 55 told Reuter by telephone from her home in Bulawayo: "I am still scared. But they have taken my passport and I have nowhere else to go."

Mrs. Nkomo was detained for two days last week after beeing picked up while traveling to Harare, the Zimbabwean capital, to catch a flight to London. Her son Tulani, daughter Thandiwe and son-in-law were still in custody, Reuter said.

For several months, Mugabe's forces have been conducting sweeps throughout Matabeleland, where Nkomo's Zimbabwe African People's Union is centered, in a search for dissidents seeking to undermine the government. Reports of rampant killings by the government troops have been denied by Mugabe, who has also asserted that he had no reason to order Nkomo's assassination.

Nkomo today dismissed those assurances, saying, "That sounds very nice, but his boys almost got me switched off."

His condition for returning home, he said, is "face to face" assurances from reliable government officials--not necessarily Mugabe--that his life will not be threatened. Shamuyarira said today no such assurances would be given unless Nkomo returned home first.

Nkomo apparently is undecided about his immediate plans. In London, he will be given round-the-clock police protection, but British officials have let it be known they prefer that Nkomo settle elsewhere. Prime Minister Margaret Thatcher's government negotiated the independence of Zimbabwe, ending the war there, and is seeking to maintain good relations with Mugabe.

While the excesses of government troops in search of Nkomo supporters are not minimized here, the British believe that whatever leverage remains on Mugabe will be forfeited if London were to become an active opposition propaganda base. For that reason, Nkomo has been given a short visa, which will only be extended if he agrees to refrain from any political activity.

Other countries formerly sympathetic to Nkomo, such as Botswana and Zambia, have also made it plain that as the loser in Zimbabwe's political and tribal power struggle, he is no longer welcome.