Items left in common parts of a building, often found in places such as a block of flats, aren’t covered under the general contents cover of the policy.
However, they’d be considered under contents in the open, provided that the land or common parts are regarded as part of your home i.e. the terms of a lease will normally allow access to specific common areas.
Contents in the open are generally covered but please refer to your policy booklet for the relevant cover limit.
Important: Pedal cycles are a specific exclusion to this.
To cover pedal cycles, you'd have to include personal possessions or worldwide belongings cover, but theft from public places wouldn't be included, unless properly secured.