With a time of 3:48.40, Britain's Steve Ovett regained the mile record only a week after his countryman, Sebastian Coe, wrested it away. Racing in Koblenz, West Germany, Ovett improved on Coe's time by 13 hundredths of a second. His effort marked the fourth time the mile record has changed hands between the two runners since July 1979. The British rivals avoid competing against one another , so Coe did not participate in the race. He is scheduled, however, to run the "Golden Mile" in Brussels this weekend.