If you go to the BR Coaching Stock group on groups.io, they have a lot of resources for the 70s and 80s for the Western Region. Not timetables, but Paddington working books, train marshalling documents, and so on. You can get a lot of insight into the London end, at least, of the Western Region across the two decades, right into the NSE era (most recent is 1989).
For example they have a working book for Paddington for summer 1975 which gives a good idea of the state of play at that time.
It looks like this is a transitional timetable pending the introduction of HSTs one year later and looks like something of an anomaly compared to the standard early/mid 70s timetable.
More typical for the era is the May 74-May 75 working book, also available from the BR Coaching Stock group.
Alternatively if you have any specific questions on Paddington workings from either year I can supply them as I've downloaded a lot of the documents onto my machine so can quickly look at them.