LONDON -- "Codel Pell" came and saw London last weekend. It doesn't seem to have conquered much, however, beyond the West End theater district and Harrods department store.

"Codel" is State Department cablese for congressional delegation -- in this case five senators, led by Claiborne Pell (D-R.I.), with four of their wives and assorted staff members, for a total of 28 people.

On the way to Geneva, where the senators -- members of the congressional Arms Control Observer Group -- were due last Monday to participate in a round of briefings by U.S. and Soviet officials on the arms control negotiations, they scheduled a weekend stop in London.

The indirect routing was not unusual, said sources at the U.S. Embassy here. Of about 17,000 official American visitors here last year, an estimated 25 percent were members of Congress, their families and staffs.

Embassy sources insisted they do not begrudge legitimate congressional business. But the fact that many such visits often are little more than what one source called "shopping trips" is seen as particularly ironic in view of congressional efforts to pare embassy budgets to the bone.

Every time a Codel schedules a trip abroad, its transportation, lodging and itinerary must be arranged by the U.S. Embassy in each foreign capital visited. The embassies also are charged with escorting the delegation from touchdown to liftoff.

Much of the cost is paid by the Senate or House of Representatives. But embassy staff members complain that with the services of everyone from the ambassador to the motor pool usually involved, the diplomatic jobs that they are sent here to do often are neglected while they provide host service.

Codel Pell was described as a "typical example" of a delegation visit that used taxpayer money and embassy time. The group, including Pell and his wife; senators Ted Stevens (R-Alaska), Don Nickles (R-Okla.), John Glenn (D-Ohio) and their wives; and unaccompanied Sen. Richard Lugar (R-Ind.), landed at London's Heathrow Airport at 7:30 a.m. on Oct. 10.

There are daily commercial flights from Washington to Geneva. But the senators traveled aboard a U.S. Air Force jet, via London.

{A spokesman for Pell said in Washington that the London stopover was scheduled both because the military plane supplied by the Pentagon for the flight could not fly directly to Geneva without refueling and because the delegation normally schedules a day of rest to deal with jet lag. The delegation uses military instead of commercial planes for its flights to Geneva, he said, because of the need to have secure communications. Most such trips are made in planes capable of flying nonstop to Geneva, he said.}

{Stevens, the ranking Republican in the delegation, took sharp issue with criticism of the stopover. "They give me a pain in the butt, those people," he said. The weekend visit "may have been an inconvenience to the personal lives" of embassy staffers who assisted them, "but it didn't cost the State Department a penny, and it frosts me to have guys sitting there on easy street in London" criticizing the visit.

{Stevens and others said that while the London stopover was largely for rest, the Sunday and Monday in Geneva were intensive workdays, with no shopping or entertainment, and a 6 a.m. departure last Tuesday.}

Until Oct. 8, sources here said, embassy inquiries as to whether the senators wanted appointments arranged went unanswered. On that day, the embassy received a request for Oct. 10 meetings with Prime Minister Margaret Thatcher and Foreign Secretary Geoffrey Howe. Both were unavailable.

At Heathrow, standard practice called for the embassy to ensure that a VIP "hospitality room" was set up for the delegation's arrival. Official embassy vehicles, plus Foreign Service officers of suitable rank, were on hand to greet the dignitaries.

In central London, the group was lodged at the Churchill Hotel, close to the embassy, where double rooms cost $250 a night. Again following standard Codel practice, a hospitality suite and embassy-staffed control room were set up at the hotel for the duration of the visit.

During the day, sources here said, some members of the delegation went shopping. From 6 to 7 p.m., U.S. Ambassador Charles H. Price II hosted a reception for them at his official residence. The only British government official present, a source said, was junior Foreign Office minister David Mellor.

The senators had specifically requested that they have no evening obligations. Instead, sources said that embassy staff members were asked to make dinner reservations for the delegation, and to obtain tickets to West End plays, including "Les Miserables," Jeffrey Archer's new hit "Beyond Reasonable Doubt," and Simon Grey's "Melon," starring Alan Bates.

On Sunday morning, embassy cars and escorts took the delegation back to Heathrow for their flight to Geneva.