I will be travelling from Preston to Newcastle on a Friday in July and returning the next day breaking the journey at York for several hours then back to Preston the same day.
Your benchmark fare is the
£61.80 Preston to Newcastle Off-Peak Return, valid by any permitted route and by any train, break of journey allowed on the return leg but not on the outward leg, and the return leg valid for one month. That seems to meet your needs.
I will need to leave about 10.30 on the Friday but will need open tickets for the return trip-ok to book advance tickets on outward journey and any routing ok as long as it's not too long-more 3 hours.
You can save about 10% on the £61.80 fare by splitting into two tickets and restricting yourself to trains via Burnley (rather than Carlisle or Manchester).
Preston - Pontefract Stations route Burnley £21.20 Anytime Return (outward valid 5 days, return leg valid one month).
Church Fenton - Newcastle £33.60 Super Off-Peak Return (M-F not before 0930, break of journey allowed on both legs and the return leg valid for one month).
Total
£54.80.
Use the Preston - Pontefract ticket to and from Church Fenton.
eastcoast.co.uk shows that it is valid to Pontefract Baghill by this route.
By splitting in this way, you are restricted to trains which call at the splitting point, Church Fenton. Fortunately, many Preston - York trains do this. On the Friday, you would be able to use this combination on the 0954 or 1154 from Preston but not on the 1054, which does not call at Church Fenton. Returning on the Saturday, you can use the 1309, 1508 or 1708 from York but not the trains in even hours which don't call at Church Fenton.
Typical journey time for Preston - Newcastle via Burnley is 3 hours 40 mins.
It's worth pointing out that there's a North Country Rail Rover priced at
£72 for unlimited travel at weekends and from 0845 M-F on any 4 of 8 consecutive days over a very wide area (see this
map, more details in this
leaflet). If you intend to travel within the map on the week before or after the trip to Newcastle and York, this could be better value.