"Neil Williams" wrote
Going outwards, you don't need to concern yourself with that. Ask for
a ticket from Boundary Zone 2 to your destination. It should be issued
with that, and not a specific station, as the origin.

In this particular instance, that is probably correct. But note that (as
discussed on uk.r previously) in some situations it is (or was) possible to
get a ticket from station in Zone x to destination which costs less than
the equivalent ticket from Boundary Zone x to destination.