This softly attractive brunette is best known to British and American TV viewers as Sarah Layton in the miniseries "The Jewel in the Crown" (1984) to filmgoers as Mirabehn, the fanatical western follower of "Gandhi" (1982) and to theatergoers as Portia opposite Dustin Hoffman in the London and Broadway (1989-90) production of "The Merchant of Venice". Geraldine James has kept a low profile to American audiences, but has had an active career in her native England, on stage and in film and television. She first won notice on the London stage as Dr. Von Zandt in the 1979 production of "The