IF the British were the black sheep of the European Community before this week's summit here, they are even more so since its conclusion.Britain's stubborn negotiating stance and its success in exempting itself from two key summit agreements incensed many of its EC partners. They warned that Britain's "a la carte" approach to European unity - picking what it wanted and rejecting what it didn't - set a dangerous precedent. "If you have a community, you should try and bring about community solutions. [Britain's] selective approach is not the best example," said Nico Wegter, a spokesman for the European Commission. John Major, the Conservative British prime minister, came to Maastricht under pressure from his party's right wing not to sacrifice British autonomy for European unity. He did not. In fact, he succeeded in winning almost every point he wanted: The new EC treaty on political and monetary union does not mention a "federalist" Europe; EC foreign policy decisions are subject to unanimous approval; the British have the right to opt out of a single European currency if their parliament so chooses; and the British are exempt from EC decisions on labor and employment issues - a subject area referred to as the "social chapter." The social chapter was the most contentious issue, with 11 Community members arguing that Europe needs uniform labor laws, while Mr. Major insisted he would not roll back a decade of labor reform and thus stifle British competitiveness and cause job loss. In the end, the social chapter was struck from the treaty, and agreed to separately by the other members. Britain's iron negotiating position clearly angered its partners. "If things keep going like this, we might start to miss [Margaret Thatcher]," said French Foreign Ministry spokesman Daniel Bernard, as midnight neared on the last day of the summit without an agreement. But several EC members, including the French, also admired Britain's negotiating skill, and admitted they had had ample warning of London's objections. At the final press conferences, the weary statesmen tried to put a good face on things. The Germans, for instance, voiced conviction that London eventually would see the disadvantages of its position and fall in step with the rest of Europe. "In five years," said German Chancellor Helmut Kohl, "many of these problems we talked about [here] will have been forgotten."