After two days of driving rains, clothes and sleeping bags have been soaked, but spirits have not been dampened in the great American campout in the streets of London.

More than 2,000 stranded standby travelers - most of them Americans - have erected a small city of lean-tos and shanties in the streets around the Laker Skytrain ticket office at Victoria Station. There, under roofs of plastic sheeting and corrugated cardboard, they sat Monday night in the pouring rain singing songs like "I've been Queuing for the Laker," to the tune of "I've Been Working on the Railroad."

Signs such as "Free the Laker 1,000" and "Home Sweet Home" have begun to dot the encampment.

In the rest of Europe, the midweek travel slump made it possible for airlines to accommodate passengers delayed by the French air traffic controllers' slowdown and crowds thinned out in most airports. The controllers said they would end the job action Wednesday and vote on whether to resume it next weekend.

When the sun came out briefly yesterday, so did the wet clothing. Makeshift clotheslines were strung between telephone poles and the streets around Victoria took on a carnival air - until the rains began again.

More than 400 persons have been joining the Laker line each day at Victoria for the past week. The airline is able to fly out only 300 of them from the Victoria line each day, thus the backlog increases. A DC10 was substituted for a Boeing 707 yesterday enabling 60 more to go home. Nevertheless, standbys joining the line last night were advised to prepare for a four- to five-day wait.

An equal number of standbys are keeping vigil at Gatwick Airport, at Laker's other ticket office. There those with tents have pitched camp in a field next to the terminal. Laker sells half its tickets at Victoria and half at Gatwick.

Meanwhile, the Pan American ticket office in downtown London had received more than 200 fresh arrivals by yesterday evening who more than replaced the 100 that Pan American was able to send off earlier in the day. The first person in the Pan Am Line, Lisa Miller, of Olympia, Wash., has been waiting five days for a flight to Seattle.

About 20 Pan Am standbys are being sent each day to Amsterdam for connecting flights to Boston.

British Airways and TWA have been actively discouraging standbys by listing all flights to the United States as full. The occassional free seat on either airline has been filled by offering them to ready takers in the Pan Am line.

Tempers have occasionally flared, but they have been assuaged by the prevailing atmosphere of claim and forbearance.

Londoners, at first dismayed to see the growing crowds literally camped on their doorstep, have responded favorably, impressed by what one of them called "the most positive demonstration of the great American spirit that we have seen here since V-E Day."

Another Briton, bowler on his head and umbrella tucked under his arm, noted that "these people have created a masterful blend of two national traditions: the American pioneering spirit, and the fine British art of queuing."

The standbys have organized themselves into sophisticated systems of self-government.

In the Laker line, Anne Seymour, who is a political science major at the University of Michigan and who claims to be a descendant of Jane Seymour, third wife of Henry VIII, took charge of "the list."

The list has the ever-increasing line broken down into groups of 400. Further, Seymour explained, "We have broken the prime groups down into affinity groups of eight each so that we all don't have to stay here all the time. The affinity groups work in shifts guarding our gear and keeping our place in line."

At Pan Am, those waiting were calling themselves "the community." Newcomers that day were being given the "initiation" speech at an adjacent vacant lot.

"We have to maintain the integrity of the queue," shouted Clarence Bowie through an improvised megaphone to new arrivals. Bowie, an electrical engineer from Hyattsville, Md., told them, "This is the fastest and most efficient way out of here."

At 4 a.m. when the call for the first flight goes out, the keepers of the list check the name of each potential ticket buyer against the list and demand a passport for identity.

When the Solomon Wong family finally left the Pan Am "community" for Seattle after a six-day wait, their efforts at guiding the list through the rigors of organization and implementation were rewarded with hugs and kisses all around a resounding round of applause that awakened the sparrows in the park across the street.

Wong, a school administrator in Hawaii, had become a "father confessor" to the group.

"I guess because I have kids of my own here," he said with a smile, "some of the other youngsters have been coming to me with their problems. I've turned half of them over to Father Bill," he said, pointing toward a Roman Catholic priest seated on a pile of cardboard chatting with a teen-ager. "Between the two of us we seem to have them reassured that they will all get home - sometime."

Londoners have reacted by bringing tea and sandwiches. One woman in the Victoria neighborhood invited a half-dozen of the senior members of the line into her home to sleep on couches instead of the sidewalk.

A modern languages professor from Notre Dame, William Richardson, received assistance from one local resident who sent around a Rolls-Royce to pick him up.

Evangelists from half a dozen Christian organizations as well as the Jewish Lubovitch Mizpah campaign walked along the line offering comfort for the soul, if not the body. A Greek Orthodox priest en route to Chicago from a monastery in Greece told fellow standbys that he had been "praying assiduously to St. Jude, the patron of hopeless causes, ever since I first signed that wretched list six days ago."

Local businesses have not suffered by the situation: The Woolworth store across from Victoria has exhausted its supply of plastic sheeting and air mattresses.

Nearby pubs were doing a boombing business, as was a second-hand furniture store which had sold out all its low-priced arm chairs - several of which could be seen dotting the sidewalk.

A pair of sidewalk tenters arranged their tents to face each other and set up a chessboard in between.

"People are surviving," said Laura Siff, a teacher from Richmond, "because many of them are campers and they know how to handle themselves in these kinds of situations." Siff, who was taking her shift in line for her affinity group, sat on a stack of old newspapers and embroidered a pillowcase - "third one I've done this week."

Siff's traveling companion from Richmond, Maxine Harman, passed the time by writing out invitations to a party she was planning for the flight home.

"We've all become such good friends here," she said. "We can't just get on the plane and read Newsweek."