A complicating factor I discovered during my latest attemptS to book cycle tickets for a Fri/Sun weekend trip:
Cycle reservations don't necessarily appear at the same time as person tickets for the same train.
The Friday tickets were released abundantly in advance and could be booked when I first try.
No success with the Sunday one "restricted" says bod at Naaarch station where I was killing time.
So I ring GWR and are told that the tickets aren't yet released, and it varied blah blah blah. In short, they couldn't book me the tickets even at 7 weeks out from the journey though they did suggest (and I'm not sure I believe it) that M-F cycle tickets are released 10-11 weeks in advance (not 13 weeks like the person tickets) and weekend ones more like 8 weeks.
I tried again in person at my local station with a mere 5.5 weeks to go, still nada
I finally got the tickets today, 4 1/1 weeks to go.
Just as well they still had some then.