Prisoner of the Judoon is surprisingly subversive for a children's show. The Judoon are authority figures whose authority stems as much from fear as from the Shadow Proclamation, and who behave quite unreasonably - their deference to regulation as much as their inclination for summary execution (and tendency to get deflected from it as well). Meanwhile the Androvax, while definitely a genocidal villain, is given a realistic motivation which comes close to being a sympathetic treatment. Not all policemen are your friends, children; not all bad people are irredeemable.
On the series format as a whole, we are heading in the dirction of the Clyde Langer adventures, which I think recognises Daniel Anthony's talents. Elisabeth Sladen did not sound totally at ease doing the series intro. However, she clearly had a ball being the Androvax in Sarah's body - much more exciting than being possessed by spiders, Mandragora or Eldrad. And the fun plotline in this series is obviously going to be letting Rani's parents in on the secret of alien activity and their daughter's involvement in it.