Originally Posted by
stut
VTEC have tried to charge me £3 because a Great Northern ticket office didn't know how to issue reservations on an obscure weekend day return ticket form Peterborough to York..
I'm honestly not sure what that was about. National Express, when they had the East Coast franchise, used to charge a reservation fee. That, as far as I know, disappeared when they did.
As far as I know, reservations for seats are now usually free (seat and berth reservations on the sleepers can sometimes be charged).
For the OP, if you do reserve before coming to the UK there's a fee charged by the BritRail retailer, but doing it at a station once you're in the UK is free of charge.