Cheap train tickets in UK

Advance tickets are cheapest tickets, which are one way tickets and generally not available earlier than 12 weeks before the date of travel. Advance tickets are sold in limited numbers, so subject to availability. You should buy advance tickets about 10-12 weeks in advance, if possible.

Off-peak tickets (including off-peak single and off-peak return) are the second cheapest tickets that provide more flexibility. You can virtually travel any time using off-peak tickets if your journey doesn't via London. Return portions of off-Peak Return tickets are valid for travel until 04:29 on the day following the last day of validity (i.e. one calendar month from outward journey). 

Break of journey is allowed on the outward portion of Off-Peak tickets and in all cases on the return portion of Off-Peak return tickets. You may start, break and resume, or end your journey at any intermediate station along the route of travel on Off-Peak tickets unless the ticket restriction for the journey you are making does not allow it. If you intend to start, break and resume, or end your journey at any intermediate station, please call 03457 4849 50 to check if it is available on your specific journey.

Any time tickets are the most expensive tickets.

You can also buy the Family & Friend railcard if you travel with family to save 1/3 off the tickets. The card is valid for one year and costs £30 (£27 if you buy it online). After a couple of trips, the card will have paid for itself.