In May 2000, CBS aired "The Linda McCartney Story", a made-for-TV film based on the 2000 biography "Linda McCartney: A portrait" by occasional friend Danny Fields.     A solo show, as I give some general impressions on the film, the leads Elizabeth Mitchell ("Frequency", "Lost") and Gary Bakewell ("Backbeat").   Between the commentary, "thumbs up" and "thumbs down", look there are interview clips comparing and contrasting the real article with these fictional counterparts.