No need for cycle reservations, at least south of Cambridge, although
the times you can take them on trains is getting a bit more
restrictive.

Mizter T wrote:
Print@Home tickets - see https://www.printtraintickets.com/ or
https://www.printtraintickets.com/one for the 'one' specific site.

Though getting off early at Tottenham Hale would be against the rules -
though you could well get away with it as long as there's not any RPIs
there. There doesn't appear to be any specific restriction about using
a bike with a Print@Home ticket, but I dunno what the story is with
regards to bikes on 'one' trains from Cambridge to London - if you need
a reservation they might not give you one if you've got this cheap
ticket, however there appears to be nothing in the T&Cs about cycles.