Where bought before travel, or on the train where there was 'no opportunity to buy' before boarding a train.....
[QUOTE='The Manual' (FRPP)]Change of Route
National Conditions of Carriage, Condition 13, permits customers to travel by a route, from the one stated on the ticket, or allowed by conditions of the National Routeing Guide, to make their journey on payment of an excess fare. The excess fare is calculated as follows:
Single tickets
The difference between the price paid and the price of the cheapest Single ticket, available for immediate travel, that allows the customer to travel on the route and Train Company of their choice.
Return tickets - Change of route in both directions
The difference between the price paid and the price of the cheapest Return ticket, available for immediate travel, that allows the customer to travel on the route and Train Company of their choice.
Return tickets - Change of route in one direction only
Half the difference between the price paid and the price of the cheapest Return ticket, available for immediate travel, that allows the customer to travel on the route and Train Company of their choice.
....[/QUOTE]
Note: An advance fare would be subject to a further £10 admin fee as it would be a change of travel plans.
Where there IS an opportunity to buy before boarding a train and it is not taken....
[QUOTE='The Manual' (FRPP)]Change of Route or travel on a day/train for which the ticket is not valid
Charge the difference between the fare paid and the cheapest single or return, available for immediate travel, for the journey being made. Railcard holders are eligible for a discount only if the original tickets were discounted.
....[/QUOTE]