Browsing the Jan 1959 Trains Illustrated I came across a report on the press trip on the first part of the Styal line. There's a map that was issued at the time showing stages of electrification which includes a number of lines that weren't part of the eventual scheme such as Walsall to Rugeley and Lichfield, Birmingham to Lichfield, Coventry to Nuneaton, Rugby-Leamington-Coventry, Swanbourne-Bletchley-Sandy (link with GN line) and Camden to Broad Street (AC presumably). Also says that the Dudding Hill loop would be electrified to give access to a depot at Cricklewood.