No, I didn't know about the second movie. I only became aware of "Mrs. Minever" about 8 years ago; my sister was staying with me when I had my knee surgery and it happened to be on AMC and she insisted that we watch it.
I first saw Mrs. Miniver after 9/11 when I heard it mentioned by Rudy Guliani, I think it was. I mentioned it to my mom and she told me how much I'd enjoy it so I went to the library and they had it.
Since then I've watched it 3-4 times (something I rarely do) and once when I was renting it from the library I noticed it's companion. I think it's called The Minivers. You'd enjoy it.