Do you know this book?

I’ve read thousands of books, and unfortunately I’ve forgotten many. There is one that I read in elementary school that was different and distinct, but I have no idea of the title, author, or resolution.

The story took place in England in WWII. Children from London were being sent to the country to be kept safe from the bombings. The story, as I remember it was that children met at a bus station (I guess it could have been a train station) in London. Two girls met in the ladies’ room and realized that they looked alike. For some reason, they switched places.
I seem to remember that when they met again, one wanted her old life back and the other didn’t. I can’t recall anything else about that book, and I would like to read it again as an adult.

Sound familiar to anyone?

Could be Searching For Shona.

I don’t know. I looked at a preview, and there was nothing familiar about it.