The Greater Washington Board of Trade auditioned its foreign business development show here last week and won favorable reviews from a polite but attentive audience of British business executives.

But the real test of the board's first mission abroad to attract investors to the Washington area is yet to come, and that could take months, years, perhaps. The highly competitive contests among state and local governments -- Maryland and Virginia agencies among them -- to lure business to their jurisdictions are seldom decided on the basis of a single marketing extravaganza for potential investors.

After conducting a seminar on investment opportunities for the prestigious London Chamber of Commerce and Industry (LCCI), however, a 10-member Board of Trade delegation returned to Washington, confident that it had achieved an initial success.

In fact, several members of the group will remain here and visit other European capitals individually after being invited by representatives of several firms, who expressed strong interest in holding further discussions.

"We have 15 to 20 appointments lined up over the next few days," said Daniel J. Callahan III, president of Washington's Riggs National Corp. and chairman of the board's business development bureau.

A board official later confirmed that the seminar had served as the basis for 14 firm follow-up meetings with London chamber members over the weekend.

The focus of those meetings, like that of the seminar, which attracted about 75 persons, was on investment opportunities in high technology, financial services, real estate development and light industrial facilities.

Although some LCCI members said they attended the seminar primarily out of curiosity, several said they came away with considerably more interest in learning more about investment opportunities in metropolitan Washington.

"To have such a very high-class and important delegation such as this meant a great deal to our members," said Ian Weatherhead, director of LCCI's North American section.

"They are all generally interested in investment opportunities in the greater Washington area. We found more interest in this particular area than any other state that we've been dealing with," Weatherhead said.

At least 10 states have sent delegations here in response to invitations from the London chamber during the past three years. The invitations generally are prompted by the degree of interest that chamber members indicate in investment opportunities in a given state.

While most business development missions are sponsored by state or local government agencies, the Board of Trade's delegation was the first private business group to be extended an invitation by LCCI.

That fact alone could have a significant impact on the outcome of his delegation's visit here, according to R. Robert Linowes, chairman of the Board of Trade's International Committee.

"To the best of my knowledge, this is the first time that a group of businessmen from metropolitan Washington has met face-to-face with foreign businessmen to talk about investing in the area, and that's significant," Linowes remarked.

Linowes said the board plans to broaden its international business search by holding similar seminars in other European capitals. In the meantime, he said, the next "Executour" to be held in the Washington area will probably include visits by several foreign businessmen.

The major selling point in the board's seminar here and one that will surely be pushed in similar meetings is Washington's rapidly increasing development as a major commerce center. And although the delegation apparently accomplished its goal of stimulating interest here, perhaps the most effective arguments for investing in the D.C. area were made by two Englishmen working in metropolitan Washington.

"I can assure you that the Washington area is nothing short of superb," declared W. B. Regan, a Northern Virginia builder who moved from England six years ago. An equally strong endorsement was volunteered by Leo J. Shefer, an official with British Aerospace USA.

The cost of exporting its highly acclaimed "Case for Washington" business development program to this foreign capital will run from $12,000 to $18,000, the board estimates. The cost would have been substantially higher, but members of the delegation voluntarily paid their travel and lodging expenses in addition to contributing about $1,000 each to the budget for the seminar.

The board's gamble in expanding its business development program could produce substantial economic gains for the Washington area in the long run. But its bid for British investment dollars comes at a time when the economy here is undergoing severe pressure from a decline in the industrial base.

Indeed, Great Britain's economy has been disappointing, the board's delegation was advised in a briefing by American embassy officials here.

Although record high inflation has cooled off, unemployment remains above 13 percent despite a slight decline last month.

And while the economy is expected to grow about 1 percent this year, a major business group here predicts a more pessimistic 0.5 percent increase.

But despite the problems with the economy, U.S. officials here see no indication of much change in the United Kingdom's status as the United States' fourth-largest trading partner. What's more, said one U.S. official, "There is tremendous interest, particularly among U.K. businessmen, in investing in the United States."

Weatherhead not only agreed with that assessment, but bristled at reports on the state of the economy.

"As far as the British economy is concerned, certainly since Margaret Thatcher took office," he insisted, "this country has never been in a balance-of-payments deficit."

Weatherhead argued that the continuing decline in the inflation rate will stimulate the economy. And when that occurs, he maintained, "British companies will be able to borrow more money and invest in their companies. . . . And it bodes well for foreign investment."