In this scenario, you will be driving 377201/204 from Milton Keynes Central to East Croydon as far as Wembley Central. Year 2016. The following requirements you will need will be:

Alan Thomson:
WCML South v5.2
Class 390 Farewell Pack

Steam:
Class 66 Pack 3 (EWS)
Chatham Mainline
Class 378
Class 390 (Discontinued)

Just Trains:
IWB Cargowaggon Pack
Voyager Advanced 2019

Armstrong Powerhouse:
Class 375/377 Enhancement Pack
Class 350 Enhancement Pack
Class 66 Enhancement Pack

Backdated Trainsim:
Virtual District Line (for the 73stock)