"Mizter T" wrote

However having just thought about it, I don't think there are any
period return tickets (as opposed to day return) in the south east
that are cheap enough for the railcard-discount of a third to result
in the fare coming in below £13.

There are some, e.g. Reading to Oxford Off-peak return GBP 14.30, out
Saturday return Sunday with Network Card GBP 9.45, out Saturday return
Monday GBP 13.00, out and back Saturday (Off-peak Day Return, with Network
Card) GBP 4.95.

Peter