THE ROYAL OPERA PERFORMANCE OF `LA BOH`EME' will be relayed live for the first time in Britain on June 9 and 12. Transmission to a giant screen on the Covent Garden Piazza will enable some 4,000 people to see the Puccini opera, free. The production willinclude such international singers as Pl'acido Domingo and Ilona Tokody. A PLASTER BUST OF THOMAS JEFFERSON sold Friday for $2.86 million, the highest amount paid at auction for a portrait bust, announced Christie's in New York. The sculpture, by Jean-Antoine Houdon, was used as a model for the Jefferson nickel. The previous record for a portrait bust and for a work by Houdon was a white marble bust of Benjamin Franklin that sold for $310,000 in November 1975. CHARLES LUDLAM, a recent Obie Award recipient for distinguished achievement in theater Off Broadway, died Thursday in New York. He was an avant-garde playwright, actor, producer, teacher, and founder of the Ridiculous Theatrical Company.