Gotta admit, I'm kinda down on the second part. The bulk of the episode seemed muddled and swerved aimlessly toward the Eiffel Tower and warehouse / presentation showdowns. Mostly, though, what did Ada Lovelace and Noor Inayat Khan's inclusions add to the story?
No, I'm not whining about female historical figures as companions, because that's awesome and we need more of that please. What I mean is, they were nothing more than sounding boards for The Doctor to explain things to in the absence of her "fam." They could have been literally anyone, historical or otherwise. When they had the opportunity to add something without The Doctor's presence, it took them all of 30 seconds to find The Master's TARDIS. And, sure, by meeting Khan The Doctor had access to a spy's telegraph, but she could build something like that in her sleep.
Then again, maybe I missed something relating to the Kasaavins being time-spies and that's why Khan and Lovelace were integral to the plot.
Can we also not do another Gallifrey-based mystery? So much time was spent on The Doctor believing himself to be the last living Time Lord only to learn he actually saved his people (2005-2013), to the whole confession dial thing (2015), I feel I need a big break from anything doing with her people. Even that five-year gap doesn't seem long enough.
All my moaning aside, it was really good to see the companions companion-ing even in the face of never seeing The Doctor again. Whenever The Doctor is not around, the companions should know what to do to gather clues and solve mysteries.