Review of all 3 episodes:
Ideas from script editor Andrew Cartmel were meant to form this story and reveal dark pre-history of the Doctor from times before the First Doctor that viewers knew. These ideas were dropped as Showrunner John Nathan Turner apparently felt it was 'revealing too much too soon' and wanted to drag the storyline out much longer. However, the show was already threatened with cancellation so this tactic was actually leaving the story to be explored in an unknown, uncertain future. Sure enough the show was taken off the air for many years and the ideas of pre First Doctor dark history would be left for novels/spin offs and unexplored in the TV show until 2020 when Chris Chibnall created his version of the idea.
Ghost Light was written by Marc Platt starting with some ideas from the previously planned story but changing it completely. The result is a muddled and confusing story but it does have an enjoyably dark and sinister atmosphere and some good elements. Instead of the Doctor's dark past we explore Ace's dark past and the best part of the story is the psychological aspect of Ace's past trauma and how it links into the story set 100 years before her experience in a derelict mansion. Here we see the mansion in the 1880s with very strange goings on and aliens in the cellar.
The creepy atmosphere, Ace's unease as she starts to feel an evil presence and the intriguing set-up of the mysterious residents in the first episode is the strongest part. It already feels slightly muddled but is a really solid, interesting episode. The second part starts to get more muddled and strange but still maintains some great threads of interest about Ace's involvement and the mystery of the house and some great gothic horror stuff. Part 3 turns into a rather camp, bizarre and confusing mish mash of ideas that are not fully formed with a villain who is quite ridiculous. It still has some good, enjoyable horror feel and strong scenes, mainly the climax of the story thread of Ace's past trauma in the house. Sophie Aldred is great and some of the guest cast are good too but it is all rather bonkers and there are some over the top performances, particularly from the silly, unconvincing bad guy.
Rather jumbled but atmospheric and interesting serial overall.
My ratings: Part 1 - 8/10, Part 2 - 8/10, Part 3 - 7.5/10. Overall - 7.83/10