VANCOUVER, OCT. 17 -- "Hang in There, Maggie," exhorted the streamer towed by a small airplane that managed to breach heavy security to circle over the buildings where Commonwealth countries were meeting here.

Not that British Prime Minister Margaret Thatcher needed the airborne words of encouragement. Without apparent help, the "Iron Lady" managed quite well in pressing an agenda on 48 former British colonies that steered away from their emphasis on apartheid and human rights to a sharper focus on trade and economic problems.

Her spokesman gloated about a new, toothless Commonwealth position on South Africa that was heavily influenced by Thatcher's resistance. And Thatcher said, "They are making a great deal of noise. There are 10 pages of communiques about it, but look through those pages, just tell me one extra sanction that they are actually going to put on. There is not one. At the end, they're going to set up a committee. We have had those before."

Canadian External Affairs Minister Joe Clark remarked that the world was suffering from "temporary sanctions fatigue," which he said seemed to result from the censorship inside South Africa and a stepped-up international propaganda campaign by Pretoria.

The conference did oust the new Fijian junta from the Commonwealth, not because of the reprisals against Indian citizens that concerned Indian Prime Minister Rajiv Gandhi, but for the technical reason that Fiji's decision to sever ties to the British monarchy during the five-day conference was automatic cause for expulsion.

But, again at the urging of Thatcher, a brief statement on Fiji left open the possibility that the new "Fijian Republic" could be readmitted if it applied.

The refusal of Britain, South Africa's largest trading partner, to go along with economic sanctions was attacked in routine fashion by African leaders and other nations.

"Without Britain, {sanctions} will work," said Clark. "There is more to the Commonwealth than Britain. There is more to the world than Britain."

Tonight, Gandhi harshly compared the split between Thatcher and the rest of the Commonwealth to the divisions inside Britain during the rise of Adolf Hitler. He strongly implied that Thatcher's views on apartheid resembled Prime Minister Neville Chamberlain's efforts to appease Nazi Germany.

Zambia's President Kenneth Kaunda said, "Leaders like {Thatcher} in the West will wake up one day and find their investments on fire."

Thatcher brushed aside the criticism, saying Kaunda and other African leaders who publicly criticized her often privately expressed a gratitude for the financial support and military training that Britain provides them.

"There wouldn't be a Commonwealth without Britain," Thatcher said.

British officials pointed out with satisfaction that Kaunda had said in a speech that "nothing can be more menacing to little children in the whole of Africa than the debt burden."

As for the Canadians, British officials deflated them with statistics showing that trade between Canada and South Africa had soared in 1986, the year after a Commonwealth conference in which Canada also had crusaded for tougher sanctions. Canadian officials responded that the two-way trade had dipped so far this year.

When a Canadian reporter suggested that the African National Congress might overthrow the white South African regime, Thatcher's spokesman responded, "It is cloud cuckooland for anyone to believe that could be done."

The "Vancouver Declaration," the major statement of conference policy, strongly supported the Uruguay Round of international trade negotiations and declared agreement "on the crucial need for reform of all trade-distorting agricultural policies, both domestic and international."

The conference also pledged assistance to Mozambique and the "front-line" southern African states such as Zambia, with economies and transportation networks tied to South Africa, that are suffering economically from retaliatory sanctions imposed by Pretoria.

Canada announced that it was writing off the equivalent of $260 million in outstanding loans to English-speaking African countries. At a Francophone summit in Quebec in September, Canada promised to forgive the equivalent of $244 million in loans to French-speaking nations in Africa. British officials declared support for a mixed package of loan write-offs and extensions and a lowering of interest rates.