A British High Court ruling Wednesday will make Lloyd's of London investors ''pay now, sue later."

In what was described by Lloyd's as "a significant ruling and one which will produce positive benefits for the Society and its members," the court upheld the "pay now, sue later" principle contained in investors', or Names', contract with their Lloyd's agents.Names had claimed the right not to pay their debts until prospective litigation alleging fraud by their agents, who managed Names' underwriting activities, had been settled. A test case to decide the matter was brought by Lloyd's managing agent, Marchant & Eliot Underwriting, against Andrew Higgins, a member of one of its underwriting syndicates.

Mr. Higgins will now appeal the High Court's decision.

''We are disappointed that once again we have to go to the Court of Appeal in order to establish a fundamental point of law. It appears that the lower courts have still not grasped the importance of European Law. We believe Lloyd's is in breach of the law and the agency agreements are therefore

and void," said Christopher Stockwell, chairman of the Lloyd's Names Association Working Party.

The ruling means agents will be able to legally enforce collection of Names' debts immediately. Where Names have persistently refused to pay their losses, agents will be able to pursue them through the courts.

About 350 writs are expected to be served by agents on defaulting Names this month alone. After that, thousands more Names could receive writs from their agents in a bid to recover millions of pounds in unpaid cash calls.

Collection of this money will go a considerable way to alleviating Lloyd's current cash flow problem. Lloyd's has so far collected just two- thirds of the UK1.5 billion ($2.36 billion) owed by Names for the last accounting year, 1992. There were fears that the market could run out of money to pay policy claims before a settlement deal is reached with litigating Names.

Lloyd's is proposing to compensate loss-hit Names with UK800 million in return for a halt to the damaging litigation against the market and its practitioners.

David Rowland, chairman of Lloyd's said, "I am very pleased to note that the judgment affirms so unequivocally what we have always believed to be the cornerstone of the Lloyd's policy."

Lloyd's financial recovery department, which has been helping agents collect money from Names, said the ruling stood as a warning to those Names who wouldn't pay their losses. "I hope sincerely that we can begin discussions with those members and, as a result, avoid costly and time- consuming litigation," said Philip Holden, head of the department.

He stressed that legal recovery of debts would not be applied to Names who were genuinely unable to meet their obligations to Lloyd's.