The handsome, sprawling new factory of the De Lorean motor company stood idle today. Workers went about the business of closing it down. Occasionally, one would careen around the parking lot on a vengeful joy ride in the sleek, silver-gray De Lorean sports car that now becomes an instant collector's item.

For these remnants of a work force that once numbered 2,600, it was a day of sadness and anger. Yesterday afternoon they learned that hopes of rescuing the factory had collapsed when its founder, John Z. De Lorean, failed to deliver on a promise of enough money to satisfy the British government, his biggest creditor.

Then, overnight, they learned that De Lorean had been arrested in Los Angeles on drug charges, which the FBI suggested may have been connected with his desperate efforts to salvage the auto company.

"I find the whole thing ludicrous and depressing," said Brendan Mackin, a 39-year-old production foreman who has been a leader in union efforts to keep the factory operating since it was first placed in the hands of receivers last February.

For Mackin and the others, indeed for all of troubled Northern Ireland, the demise of De Lorean represents a severe blow to the dream of attracting badly needed manufacturing jobs. But with debts estimated at nearly $200 million and De Lorean himself in serious trouble, all hope of rescuing the plant seems gone.

Eric Ferguson, an auctioneer who specializes in automobiles and commercial sales, was already touring the premises this morning. He estimated that the aluminum-and- brick factory, with its high-technology equipment could fetch almost $80 million if a buyer were found. The remaining 1,000 cars will soon sell for more than the $26,000 De Lorean was asking when they were first built, he reckoned.

Ferguson expressed surprise that the British government -- having already invested at least $150 million in the enterprise -- might not be prepared to go for a bit more before giving up. In that view he was not alone.

"What happened to John De Lorean should have nothing to do with the De Lorean motor company," said William Parker a 29-year-old worker.

Parker blamed Prime Minister Margaret Thatcher's Conservative government for discarding thousands of jobs that might still be revived. It will cost the government as much in unemployment benefits over the next year, he argued, as it would to keep the factory operating while new capital is found.

"We've done a good job here," he said. "We built this factory in two years and we're producing good cars. Even with the company in trouble, 276 cars were sold in September. What happens now? We're all on the dole. There are 30 men around here chasing each new job."

But for the government, the prospect of adding to Northern Ireland's dismal unemployment figures--which stand at about 23 percent -- was plainly not enough to deter it from ending a massive flow of money to a project long gone sour.

From the outset, De Lorean's bold dream of building a gull-winged luxury roadster on the outskirts of Belfast represented a risky venture for the British. Even before Thatcher took office in 1979, the British government had put up almost $100 million in grants, loans and loan guarantees although the U.S. Securities and Exchange Commission had advised potential investors to stay away after studying De Lorean's proposal.

De Lorean himself raised about $20 million and officials now concede that the amount of private capital fell far short of what was needed to promote a brand new car.

"This always had to be regarded as a high-risk project," one British official said today. But 2,600 jobs in Belfast made it look worthwhile. This was a decision made for political and social reasons not economic ones."

Still, it looked for a time like the deal might work. The factory went up in what had been a marshland and the DMC12 began to roll off the production line. But the all-important U.S. market never developed because of the severe recession in auto sales. The British government poured in more money without significant return.

Up to now, a trade official estimated today, the government has received less than a million dollars in royalties on the car.

There were other problems. Design delays were reported on plans for a DMC sedan. Service and parts delivery were sluggish. Complaints were voiced from residents of the surrounding area that De Lorean favored Protestant over Catholic workers.

Finally, in February, Thatcher put a stop to the government funding and receivers were called in to organize a rescue bid that never succeeded. Production was halted and workers laid off, but enough interest was expressed by potential investors to keep the factory open.

The last chance was a new company called De Lorean Motor Cars Inc. of New York, but no deal was completed.

Monday night, two De Lorean associates were arrested on drug charges. Yesterday, only hours before De Lorean was picked up in a Los Angeles hotel room carrying more than 15 pounds of cocaine, the secretary of state for Northern Ireland announced that "the receivers would now proceed to the final rundown of the Dunmurry plant."

Ripples of the De Lorean failure will be felt throughout the British economy. In Northern Ireland alone, 350 creditors are owed more than $40 million and several smaller companies may go under because of the losses, Malcolm Stevens, a spokesman for the creditors said today.

"This was a government-backed venture and business people . . . had every right to regard that as a gilt-edged investment," he said.

With the closing of the De Lorean plant, 36 American companies continue to operate in Northern Ireland, employing 18,000 people, 12 percent of the province's depleted manufacturing force.

Only one other American-sponsored high- visibility, venture-capital enterprise remains. It is Lear Fan Ltd., developers of a radical new design in executive jet aircraft pioneered by the late William P. Lear, whose Learjet is world famous.

As was the case with De Lorean, Lear Fan ran into a serious capital shortage about a year ago. But with firm orders for 275 aircraft once Federal Aviation Administration certification is granted, the company raised about $100 million, according to British sources.

To protect its interests -- and help secure the 550 jobs in Lear's Belfast plant -- the British government also put up about 5 percent of the new money.

"It is unfortunate that people will see investment in Northern Ireland through the De Lorean filter," he said. "We have good facilities here, competitive costs and we desperately need the jobs."