If I'd booked for steam and it wasn't supplied, I'd expect an option of my money back if I didn't want to travel behind the diesel offered.....
Hmmm .. but their terms and conditions say
If, for reasons beyond our control, a trip advertised as being at least partially steam hauled has no steam traction a partial refund of ^10 in Premium Standard, ^15 in First Class, ^20 in Premier Dining and ^25 in Pullman Style Dining may be offered. Alternatively we may offer a credit note for double this amount to be used against a future trip. The nature of the refund must be agreed on the date of the trip, otherwise the credit note will be issued.