The ending is surely one of the saddest scenes ever to appear in the series. The Doctor locks Susan out of the TARDIS and makes a speech at her. No wonder she and David can't look one another in the eye. Of course, Time Lord "years" are different to human ones and so Susan isn't quite 16 going on 17 in the way that she might seem, but it's hard to believe that their relationship will be happy (or even a long one). Susan may also know things about the Time Lord reproductive system that may be news to David (of course, that might not necessarily be a problem).
Obviously the plot doesn't make any sense. But the sense of a city and a country under occupation is effectively invoked. We have the resistance, but we also have the black marketer and we also have the ordinary, decent folk - who will report Barbara and Jenny to the occupiers in return for a some scraps of food. Given human nature that's a scene that few of us can watch with complete equanimity. In 1964, the memory of the threat of occupation was only 20 years old (and the fear that next year it could easily be the Red Army on the streets of a nuclear-devastated capital).
Ian though at least manages to keep his suit and key on throughout. This is 1964 and perhaps Bill Russell might have thought himself unlucky not to have been in the running for the role of James Bond; he certainly offers a decent simulacra of the part. Still it is terribly incongruous to have him dressed like all the time. But, of course, it was a more elegant age.
And the Robomen are clearly there because children will be able to imitate them in the playground. Which seems an oddly Steven Moffat kind of thing to put in.
I suppose the notion of that the transport museum might contain a 1930s lorry in working order isn't that silly. It's the kind of thing that they have in museums after all. Interesting though that the Daleks are clearly allowing some kind of ongoing maintenance of the exhibits, but I suppose that is part of British "Keep Calm and Carry On" pragmatism even in the C22th that the museum volunteer would to keep everything in order: they might not have much else to do. Where Barbara got her HGV training is another matter: she's surely too young to have been in Wrens or some such. But perhaps there's a missing adventure.
Now Write On...
This one has a sequel built in. The Doctor says he will come back to visit Susan. He didn't say when or which incarnation of himself it would be. Assuming that humans still have more or less the same longevity as today in the C22nd/C23rd, Susan is going, sooner or later, to find herself a widow. And before that she may have a lot of explaining to do as she ages so much more slowly than her husband. Assuming that some crisis in newly liberated Earth doesn't lead to her overnight changing into someone else. There is plenty her grandfather could help out with.
The problem is that there aren't any Time Lords left now except for the Doctor. So we can't and visit Susan because she presumably was rubbed out of history in the Time War. And she only exists in the memory (recall the Doctor's conversation with Victoria in "The Tomb of the Cybermen"). The more I think about it the more I realise that getting rid of the Time Lords was the Worst. Idea. Ever. Because it traps the Doctor as the lonely god. We can only hope that the Moff will bring the Time Lords back again. Permanently.
Other possibilities include scenarios set in occupied areas: the resistance in WWII Europe or, in an alternative universe, an occupied Britain. Another possibility is a successful invasion. Given that the Earth is invaded unsuccessfully so often and given that the Daleks did manage to do it properly once, perhaps some species might come with a plan more cunning than even the Doctor can counter.