Thanks Dr D, glad you like the idea. The modular approach is growing on me, as long as it doesn't become too much of a straight jacket. There is also the option of doing it for the passenger side of things instead, which might be a better idea given the challenge of how to model the mainlines at Farthing in a small space!
You are not wrong of course. The difference in levels was partly inspired by this, although those are private sidings at the rear.
The railway history of Farthing is an intricate one, so perhaps the siding at the front in my track plan is an outlier siding from a lower level configuration that the GWR has decided to retain.