Excuse my English. TfL do not appear to enforce the existing bicycle restrictions on the London Overground railway service.

Highbury and Islington to West Croydon
Folding bicycles can be carried free of charge on any London Overground services at any time.

Non-folding bicycles may not be carried on any London Overground services between 07:00 and 10:00 and between 16:00 and 19:00 Monday to Friday
Non-folding bicycles may be carried free of charge at all other times

There are often non-folding bicycles on the train in the prohibited hours.