Can I choose the change point with AP tix?

[button_boxer]

Yes multiple vias would help, sometimes I've managed to simulate it by picking an intermediate point even though the train isn't scheduled to call there.
Looking at the map I guess it might be able to do something like that for Blackpool Nottingham but having quickly looked at the map it would probably be difficult to fine one that takes in Leeds and Derby so then you are left with one via point

Via Belper?

 

[Paul Kelly]

I tried Belper and Duffield but neither seem to be timing points for any CrossCountry service heading north from Derby? Or were you able to get it to work?

 

[OwlMan]

Try Wakefield Westgate - it gives advance tickets (but not via Derby).

Peter

 

[cuccir]

It is odd how it works however. Lets take the 1700 London Kings Cross - Edinburgh service, very few APs because it is a ticket from Kings Cross in the peak, however a lot of people get off at York. I am not sure if they have a quota from York - Edinburgh to resell the seats vacated from the London - York passengers, saying that they will probably have made the money on that seat anyway!

I've always noticed that East Coast tend to have better availability of advance tickets when I'm travelling north rather than south (from Durham), relatively close to the date of travel. This suggests that there's a different quota based on each stop, though this might be relatively straight forward on East Coast's network, compared to someone like Cross Country's.

However, I presume that if I booked a Durham - York ticket I would indeed be 'blocking' a potential Edinburgh to Kings Cross advance ; but someone could still book the seat Edinburgh - Durham, and York - London.