Mr. Churchill's Secretary by Susan Elia MacNeal was set in London during WWII and follows Maggie Hope, who is hired as a typist at No. 10 Downing Street.
I liked the setting and enjoyed reading about London (where I grew up) during a time period before I was born. I did find though that some of dialog didn't really fit in with the time period and one female character was nicknamed Chuck which I found stopped me every time I read it (I think of this as a boy name). It was a good read, but not one of my favorites.