The second season of Doctor Who begins with Planet of Giants. All episodes of this story exist and it is scheduled to be released on DVD later this year. Again, being impatient to watch all of the stories I've not seen, I couldn't wait. :) This story has been released on VHS, so I was able to watch that release to continue my journey.
This story was fairly good, not the best, but certainly not the worst. After seeing blockbuster movies such as Honey, I Shrunk the Kids and The Incredible Shrinking Woman which were inspired by earlier movies and TV series such as The Incredible Shrinking Man and Land of the Giants, the idea seems a little dated, but this serial predates all but The Incedible Shrinking Man, which was almost certainly an inspiration for this serial. In fact, since this serial predates Land of the Giants by several years, I'd be willing to bet that Irwin Allen based the alternate Earth idea on this serial, although it could just be an incredible coincidence. :)
Incidentally, this story was originally written and filmed as four episodes, but during post production, it was decided to merge episodes 3 and 4 to produce a tighter, faster paced story. This created a deficit of one episode which paved the way for the standalone episode Mission to the Unknown, which actually ran during the third season, but more on that later. As River Song, would say... Spoilers! :)