where "is" Callow Lane in the bigger scheme of things?
Thanks for the kind comments, Graham.
'Callow Lane' is more or less on the site of the erstwhile 'New Engine Yard', which was at the end of a Midland Railway freight-only line from Westerleigh Yard. This was built to serve the pits in the Coalpit Heath area, particularly Frog Lane and Mayshill, both of which closed shortly after the end of the second world war.
In my world, the GW built a connecting line from Coalpit Heath West Jct to link with the Midland at Callow Lane, thus allowing me to run various naughty GWR type locos and other related stuff, besides ex-MR/LMS locos.
A short spur leads to a chocolate factory, which is intended to be 'Frys-esque', as in the way the private siding to the Frys factory in Keynsham crossed the road next to the station.
Although Mayshill Colliery is indeed closed in my world, Frog Lane was modernised and survives into the early 1970s (a bit like Writhlington & Kilmersdon to the south). Changing geological history is pretty easy from the comfort of your own keyboard...
Various industrial locomotives (NCB and chocolate factory) were authorised by various unlikely LMS and then BR personages to run out onto the 'main line' at Callow Lane, to deliver and even shunt their trains.
There used to be a passenger service, including a halt at Callow Lane, but ceased in the 1920s and only the remains of the platforms remain (more remains on one side than the other, as this is also used as an unofficial walking route by railway staff).
Here's an area plan and a diagram of the layout: