The price of a through Off Peak Return is £56.50, this is valid on any train except those timed to depart Mondays-Fridays before 0415. Anything else may be less flexible and it is unclear how much flexibility you need?
"Splitting" the journey into a combination of tickets may work. Use a WebTIS website (e.g.
EC,
LM etc) and click the info (i) button next to the itinerary you want, then tick 'show all calling points', this shows the places where you could "split" the journey into a combination of tickets (note the train must call on the return journey too). For example, Preston will be the first station on the list to check.
Note that if you want to return a different day (as in your case), then unless singles are sensibly priced (unlikely in the case of shorter distance singles) it will not be cheaper to split at stations where only
Day Return tickets are available. Therefore, it is
generally only best to look at longer distance tickets, where Off Peak Return (SVR) fares can be combined.
"Splitting" isn't the only way to reduce the cost. You can take advantage of
Routeing Guide anomalies by looking for 'over-distance' tickets which you can then start/finish short, though ATOC and some TOCs are keen to remove such anomalies so if they get mentioned here that can mean the end of them. Finishing short/breaking your journey is not permitted with Advance tickets though, so this technique is only valid when using "walk on" tickets.
Travelling at "peak" times (which varies by route and ticket held) can be reduced by purchasing tickets with more favourable restrictions and either splitting and/or starting/finishing short. Again, some TOCs do not like this and can take action. Obviously that does not apply in the case of the 8th-9th of October, though it
may apply on the 30th September, depending on what time you want to travel. The through Off Peak fare is very flexible, but if you "split", you may have to depart later if using Off Peak tickets.