You may use two or more tickets for one journey as long as together they cover the entire journey[...]
(conditions regarding stopping at the split unless one ticket is a season/leisure pass)
[...]If you do not comply with this Condition, you will be treated as having joined the train without a ticket and Condition 2 or 4 will apply, either to the entire journey, or from the last station where the train stopped at which at least one of the tickets was valid.
Before you travel you must have a ticket or other authority to travel which is valid for the train(s) you intend to use and for the journey you intend to make, unless the circumstances set out in (b) (i) or (ii) below apply[...]
(conditions regarding if there are no ticket purchasing facilities).
If you travel further than a ticket allows If you travel beyond the destination shown on the ticket, you will be treated as having joined the train without a ticket for that additional part of your journey. Condition 2 or 4 will apply for that additional part of your journey.
Tickets for your entire journey should be purchased before boarding a train, unless there are no facilities to do so. If you board a train at a station, where facilities do exist, without a ticket (or tickets) for your entire journey, a Guard/Conductor is only obliged to offer the undiscounted Anytime Single or Return for the portion of the journey for which you do not hold a ticket.
Sheffield booking office routinely refuse to sell a GM Wayfarer even though they could do so quite easily (i.e. the facility to issue the ticket is there but the staff refuse to use it). I therefore no longer bother to ask and purchase one from the Northern guard on the Hope Valley stopper. No guard has ever refused to sell one, regardless as to whether they reach me before of after Grindleford.
In a thread full of red herrings and tangents can anyone confirm the answer to the original question: is an on-train ticket seller correct to refuse to sell a ticket for a future journey?
If I'm asked for a ticket, I'll sell it. As long as Avantix will allow me to do it, I don't care where it's from and to or anything. Sounds like the guy just didn't want to, to me.
Without thumbing through my TSA, I believe the answer to the question is 'yes' in the sense that the Conductor/TE is not obliged to offer a full retail service. This is only a requirement at normal, land-based ticket offices. TOCs can limit the range of tickets sold on-board as they wish.
But I agree this it is surprising that the conductor did refuse the issue in the circumstances described.
This is just a manifestation of the completely hopeless ticketing situation in the UK. People in other countries think our fragmented system is risible.
Sheffield booking office routinely refuse to sell a GM Wayfarer even though they could do so quite easily (i.e. the facility to issue the ticket is there but the staff refuse to use it). I therefore no longer bother to ask and purchase one from the Northern guard on the Hope Valley stopper. No guard has ever refused to sell one, regardless as to whether they reach me before of after Grindleford.