Originally Posted by
stifle
It is sometimes cheaper (rather than lazy) to issue from a named station rather than Boundary Zone X, and this is only a disadvantage if the Travelcard held is a Day Travelcard, in which case the combination isn't valid.
There are some anomalies, but you need to be careful if the train doesn't stop at the named station. While most train companies in the SE have pretty much always let it pass, some have now stated that they will not accept this (this was after several people discovered they could significantly reduce the cost of their season ticket by doing so - e.g. at Hadley Wood).
(FWIW, If you're using a point-to-point season ticket as part of your journey, you can split your tickets as much as you like, and you needn't be on a train that calls at that station. However, Travelcards are a special case.)
Boundary Zone X tickets are available as a wide range of ticket types (not just day returns) depending on the origin and destination in question. I don't have access to the fares database at the moment but will endeavour to look up the various options for this journey when I get a chance.
Yes, my apologies, I was skim-reading and assuming a day travelcard!