Help! I booked an advance single from Nuneaton to London for the 0735 Virgin service. I now need to travel on the 0708. I assumed (wrongly) that I could simply log into Redspottedhanky, pay an upgrade fee and change my booking. However it says that there are 'No available delivery methods available'? Why can't I simply pick up the amendment with my original ticket? Is the only option now to upgrade at a station?