In most churches, nobody expects much of the visiting summer clergyman except for him to hold Sunday services for the few faithful who turn up, conduct whatever funerals are required and, in general, hold things together until the pastor gets back in September.

It hasn't worked out that way at Georgetown Presbyterian Church this summer. There, for the last six weeks, a sandy-haired exchange pastor from Scotland has been delighting parishioners with his zestful life style as well as his preaching.

Sunday church attendance has been "extraordinary for summer" since the Rev. Campbell Gillon has been here, explained a longtime member, Mary Umbarger.

Like most Protestant churches, summer attendance at Georgetown is "usually scant as can be," Umbarger explained, but for the last six weeks that Gillon has been here, "it's been much larger," she said.

Gillon, 51, who is pastor of Glasgow's 1,700-member Cathcart Old Church ("We know it's at least 800 years old," he explained), has exchanged parishes for the summer with Georgetown Presbyterian's senior minister, the Rev. Dr. Richard J. Oman.

The Scottish pastor is as happy to be here as the Georgetown folks are to have him. "I'm astonished at the response here," he confessed to a visitor. "Week after week in Scotland you can do your best . . . " He doesn't finish the sentence. Yet hs is clearly impressed with his reception here.

"They've even asked me for copies of my sermons - they're going to print them," he observed wonderingly.

Gillon and Oman, Scotsman and American, are typical of hundreds of English-speaking clergy who swap congregations for the summer. Where such exchange works, as this one does, everybody wins.

The clergymen involved get a firsthand encounter with the way their church functions in a foreign land. Both congregations get the stimulus of a fresh face in the pulpit, and view their faith in the context of a different culture. Even when everybody gets back home in September, the benefits continue, with countless stories to tell, transatlantic friendships to flourish and, possibly, new ideas to put into practice.

Gillon, who was accompanied here by his wife and daughter, has plunged wholeheartedly into parish life here. "We had a congregational dinner one night," Mary Umbarger reports. "The place was just bursting. He led Scottish dances. His wife sang a solo and he accompanied her. And he told the best jokes!"

By way of cultural exchanges, Gillon reported, some of the church young people taught him how to do the hustle. "I can now go through three of the basic steps. Och, we've had a good time," Gillon told a visitor.

On the more serious side, the Scottish pastor found more to wonder at in the city and community than in the church itself.

"This distances!" he exclaimed - he has paid calls on Georgetown's members scattered from Potomac to lower Prince George's County. "I can see why they have two interludes in the service to let folks (latecomers) sit down."

But the meeting of the presbytery here he found "like presbyteries the world over."

The two pastors not only swapped pulpits for the summer; they also swapped cars. To his chagrin, the Scottish pastor found himself confronted, when he arrived, with "the biggest Chevy wagon they make." He is proud that he had no mishaps with the vehicle despite the added handicaps of having to drive it on "the wrong side of the road and the (steering) wheel on the wrong side of the car."

As are most tourists, Gillon has been impressed by the "beautiful buildings" of Washington. One that has struck him particularly has been the Washington Cathedral. "It's so brand new!" he exclaimed. "All the cathedrals in England are so much older."

Gillon, whose bubbling good humor puts to rest any stereotypes of dour Scotsmen, helped to introduce himself to his congregation with a Gillon family bulletin board that held a prominent place in the church vestibule. Most prominent among the family photos and self-deprecatory cartoons he drew for the display, was a photograph of his two eldest daughters, both whom are ordained clergy in the Church of Scotland, as was Gillon's father.

Gillon, who last year celebrated the 25th anniversary of his own ordination, said he had no problem writing sermons for an American congregation. "I work on the simple principle that human nature is the same everywhere," he said. "Folks are folks, joys are joys and miseries are miseries wherever you go."

What really worried him before he got here, he confessed, was how the American congregation would react to his rich Scottish accent. "I was worried, could they understand what I was saying? That's the first battle," he recalled.

He need not have worried.To the Presbyterian ear, the lilting gutturals and burr of Caledonia are as dear as Latin to the heart of a Catholic traditionalist.

After he preaches his last sermon here on Sunday, Gillon will spend a couple of weeks in Baltimore, visiting in the congregation of a Presbyterian pastor there, the Rev. Robert Hewitt of Second Presbyterian Church, who was accidentally responsible for the Gillon-Oman exchange.

Hewitt was in Glasgow last year, "I ran into him at a funeral," Gillon recalled. "We got to talking and he said he had a friend (Oman) who might be interested in a summer exchange and one thing led to another."

While Gillon left behind four weddings scheduled for Oman to perform in Glasgow, he will perform only one here - and that after a bit of a hassle to arrange all the necessary paperwork required of clergymen by the city.

Weddings in Scotland, Gillon explained, are major events for a pastor. "You start around 3:30 or 4 in the afternoon. After the service in the church, the whole company goes to a hotel for the reception.

"After the reception line, the whole company sits down to a five-or-six-course meal - none of this standing around the kirk for a half hour with a cup of champagne," he said firmly. "Then after the coffee, you begin - the minister is the toastmaster - you introduce the people, you tell some jokes, and then comes the dancing."

From ballroom dancing to Scottish country dancing, Gillon joins in. "Apart from anything else, it shakes off some of the effects of the meal," he observed wryly.

In addition to his obvious role in such affairs, Gillon sometimes find that weddings provide him with a unique opportunity for ministry. "Often, the wedding guests are non-churchgoing types.And after they've seen the minister enjoying himself like anybody else, they get a different idea of what the church is all about."

It's happened a good many times, he said, that as the dancing and celebration of the wedding feast proceed, a guest who is a total stranger will approach him for a serious discussion.

Here in Washington, members of the congregation are all but vying with each other to entertain the Gillons in their homes.

"Every day is Christmas," observed the churchman to a late afternoon visitor as he shut off the church office air conditioner - "we never use these things in Glasgow - too cool there" - and prepared to keep a dinner engagement. Och, I'm enjoying it."