I'm so glad I found this thread.
"And Then We Wrote" was the name of a one-night stand of a show,
put together by Michael Flanders and Donald Swann
(recorded, and released by EMI on the CD box set "Hat Trick")
which I have listened to from beginning to end.

The first time Flanders and Swann -- according to their account --
got a piece into somebody's West End revue in the 1950's,
the revue was titled, you guessed it, "Oranges and Lemons,"
produced by Laurier Lister, partner of Max Adrian.

The tune they put in was
a particularly sharp parody of Gilbert & Sullivan
called "In the D'Oyly Cart."

And now I know where "Oranges and Lemons" got its name. Thank you!