Many thanks for the various responses given, and time taken to write them. Point about it being more appropriate in the other forum noted, and if any admin wants to move it then be my guest!
To answer the questions;
A-B and B-C can both take around 3 coach lengths, which for the 'lower section station' is sufficient, as the looped platform can only take this. The 'lower section' is a separate station and yard area, rather than it being an MPD as Jeremy speculated. My main 'aim' is that trains can move across any of the three stretches of track to get to either the 'main' layout or lower station, or continue on the main layout, rather than multiple train movements needing to be controlled over this section of track in a short period of time. From your advice, it would seem that an auto reverser planted as per Harlequin's suggestion is the best move for my intended operation.
Many thanks to everyone for your help.