According to IMDB, both Mary Tamm and Lalla Ward have uncredited appearances in The End of Time (not sure if Part 1 or Part 2). Does anyone know where they are in the episode?

Mary Tamm: Romana I, Lalla Ward: Romana II. Episode in question - the last David Tennant episodes. I think they may have been in the Gallifrey scenes as Timelord High Council, but I wouldn't put it past Russell T Davies to have them in random cameos just as a nod of respect to the past.