There is a book about Barking MB. Can't recall the name. My secondhand copy fell to bits. I remember the author stating that borough elections were noncompetitive/uncontested whereas county divisions were keenly fought because of the boundaries.
"Town councillors: a study of Barking" by Anthony M. Rees, Trevor A. Smith. Acton Society Trust, 1964. Several copies on Abebooks going for peanuts.