Just seen this: We went on a few Merrymakers from Scunthorpe in Humberside, as was, in the early 70's, a few of which went through Birmingham. They ALWAYS took the avoiding line at Saltley, usually waiting at signals there for a crew change. If you were lucky you saw the occasional electric pass overhead, and once a Western coming off New street in the dark, heading to Saltley. It was a warm night and we had stood for ages, but we had powerful torches so the Western was captured for posterity.
What sticks in my mind is staring out of the carriage windows in the vestibule, window down, hoping something would come before we moved off. We heard the Western coming well before we saw it. Been to Cardiff, IIRC.
The neon sign, "Landore Street Carpets" also sticks in my mind for some reason. Wonder if they still exist?
Funny, the trips always came from Cleethorpes, and featured an Immingham crew to start with, but were almost always a 45, none of which were allocated to Immingham.