A thought for Bootle: you could model the junction on a day where, for whatever reason, the line via Ormskirk is closed, so expresses and semi-fasts are diverting via Southport and Burscough North Junction, as definitely happened a few times in the late 1960s.
In the 1967-68 period, this would give you a combination of...
- Classes 104/105/108/110/112/113 DMU.
- Diesel classes 24/25/40/47/50
- LMS black fives, BR standard fives, Britannias.
And that's just passenger services! Up until 1968 there was still a little bit of freight coming in from the lines around the Docks to Preston and Blackburn, which on a diversion day would also have run via Bootle/Southport/Burscough, so that allows for a few more BR steam classes.
Liveries-wise, you have BR green and full BR blue with full yellow ends: plus various intermediates: blue with small panels for the DMUs and 502s, green with full yellow ends for the diesel locos, and various levels of grime for steam! Coaching stock would be a complete mix of maroon and blue/grey, predominantly mk.1, but with a few early mk.2s and some LMS and LNER survivors. Believe a few SR green coaches were also drafted up to the NW in about 1967 and survived a couple of years before repainting, for additional variety.