I came across the ticketsplitter tool on Martin Lewis’s Moneysavingexpert.com website. Basically it allows you to save money on rail fares by providing you with information on how to split your journey into single tickets which when combined together could be cheaper than the full single fare. At the moment it only works for walk-on fares, but you can get an indication of where to split your journey which you can use when purchasing advance tickets.
For instance, 2 weeks ago I booked an advance ticket from Nottingham to Glasgow. The lowest standard advanced price quoted on thetrainline.com was £57. However by using ticketsplitter tool I found out that the journey could be split in two parts – Nottingham to Lancaster, and Lancaster to Glasgow. The price of an advanced ticket Nottingham to Lancaster was £22, and from Lancaster to Glasgow £13. When combined (£35) this compares favourably with the standard single fare of £57.
However you have to ensure that the train you are due to travel on stops at all the stations on the tickets. In my case I can join the London to Glasgow train at Preston which covers the Nottingham to Lancaster section as the train stops at Lancaster as well, so I can remain on the train. You have to ensure that you have the Lancaster to Glasgow ticket already on you, as the train only stops for 1 minute at Lancaster, preventing you from collecting your ticket from the ticket machine on the platfotm! So arranging to have the tickets posted to your home address in advance of the journey is advisable.