The PP was intended to be a Police Pistol, and the PPK was developed from the PP, some say the K is for
kurz (short) others say it stood for
Kriminal, signifying it was the smaller "detective special" gun. There are books about them, interesting reading if that's your thing.
It's been ages since I read the Bond books and the movies aren't quite the same though they do get some of the books "right" in places.
Bond was given the PPK in .32ACP and told that it "hits like a brick through a plate glass window". I suppose, compared to the .25 he had before, it did, but Ian Fleming really didn't know much about guns.
If I remember right, the .38 came from a friend of Bond's an American, with their CIA. It was referred to (by the Brits) as "a cannon".
And yes, ineffective against a flamethrower tank....
The Gun Control Act of 1968 forbid the importation of the PPK, it missed the size requirement by 1/4" or so and Walther created the PPK/s essentially putting the PPK slide on a PP frame. PPs were not banned by that law, they were big enough to comply with the limits in that law, and could have been imported afterwards, though I have no idea how many were, if any.