Here’s a scenario I made that follows service 1M27 from Brighton – London Victoria.

Required Routes:

Route – London to Brighton – http://store.steampowered.com/app/208280/
Route – London to Bedford – http://store.steampowered.com/app/277760/
Route – South London Network – http://store.steampowered.com/app/222638/
Route – North London Line – http://store.steampowered.com/app/325974/
Route – London to Faversham – http://store.steampowered.com/app/222557/

Required Locos:
FCC Class 377 – https://store.steampowered.com/app/222541/
GX Class 442 – https://store.steampowered.com/app/277773/
Class 158 (Comes with route) – https://store.steampowered.com/app/376941/
SN Class 171 – https://store.steampowered.com/app/208364/

Class 66 – Comes with London to Bedford Route
Class 456 – Comes with South London Network Route

Please read the README for instructions of how to install scenario.