So how can the customer be responsible for errors made by the retailer? If the train ticket is sold in conjunction with an itinerary, it naturally follows that the ticket is valid for itinerary.
Yes, that's what we have said; if you are following the itinerary, you should be fine.
Of course following an itinerary that is not intended to be valid is unlikely to be hassle-free and
could have all sorts of negative concequences, depending on the reasonableness of what you are doing and also how you interact with the staff.
In addition, the terms of the ticket type Anytime Day Single means I am not tied to the times of the itinerary as well.
Feel free to make that argument if you become embroiled in a dispute; I know of someone who got into such a dispute and chose not to let the matter go to court and so they paid a settlement to the company (the ticket was issued between two stations in the Midlands and was used via Aberdeen, if I recall correctly; the ticket was not being used fully in conjunction with the itinerary and the passenger initially made the argument that you are stating before giving up).
If you fought your ground and the matter went to court, I would strongly advise you do not represent yourself but instead pay for proper legal representation; it would be a matter for the court to decide if you are right or not but until then, I wouldn't take it for granted.
Providing you are happy to stump up the solicitors costs (which could be well into four figures), feel free to give it a go, but if you don't have a few grand spare, I would not be risking it! But this is straying well beyond the subject of this thread.