I purchased an advance ticket for the Sleeper from London to Penzance shortly after they became available for my travel date in June. Its only when I've come to collect the tickets this week that I've realised i've only purchased a seated advance ticket and not one of the Sleeper Advance Solo Packages which includes a berth. There are still higher priced quotas of the Berth Advances on the train I am booked to travel on so I thought I would just be able to head down to my local station and exchange my advance for the one I wanted with a cost of the upgrade to advance berth ticket available (£64 - ticket already held) + £10 admin charge = £74 Instead all they were able to offer me was an upgrade to the Super Off Peak Single (£62 - ticket already held) + Sleeper solo supplement £50 + admin charge £10 = £122 This would cost me more in total than just simply buying the berth advance available currently and writing off the original ticket so obviously I said no thanks. My next step was to send an email off to FGW to check that what I was being offered was correct, FGW have replied to my query stating that the ticket office was correct and I can't exchange to an berth advance. Does anyone know if it is possible to exchange to a berth advance from a seated advance ticket or if a workaround would be if I exchanged to a different nights berth advance and then exchanged back to my desired service?