I expect to be travelling on the return portion of an off-peak return (SVR) from Shotton to Cardiff on Saturday, and intend to travel with WSMR between Wrexham and Wolverhampton, in first class on that leg only. Am I correct in thinking:
Excess payable will be the price of a FDS ticket less a SDS, i.e. £13.55 - £8.70 = £4.85? (with a railcard)
The FRPP states the following with regard to excess fares when a passenger wishes to upgrade to first class:
FRPP said:
The Excess Fare to charge when there was “no opportunity to buy” before boarding the train
Transfer to First Class accommodation
National Rail Conditions of Carriage, Condition 39, allows a customer holding a ticket for travel in Standard accommodation to travel in First Class, on payment of an Excess fare. General principles for Excess fares are:
...
Return Tickets
a) Travel in one direction
Off-Peak/Off-Peak Day, Super Off-Peak/Super Off-Peak Day = difference between the fare paid and the Standard Return plus the difference between the Standard Single and the First Class Single fare for the same route. If cheaper, the First Class Single fare.
So lets apply the above specifically to
krus_aragon's situation.
Firstly you cannot just excess your ticket for the portion of the journey you will be travelling first class under. You will have to excess the entire leg.
The cost of excessing the entire return leg will be
difference between the fare paid and the Standard Return (0.00, the Standard Return fare between Shotton and Cardiff is the SVR which is in fact the only Standard Class return ticket available) PLUS
"the difference between the Standard Single and the First Class Single fare for the same route" (£69.40 FDS - £48.50 SDS = £20.90). So the excess will be £20.90,
krus_aragon does have a 16-25 Railcard but in this specific circumstance the Railcard does not garner any discount.