A header bar assembly has a row of header bar elements mounted on a fixed header bar section. The assembly includes a first moveable wing having mounted thereon one or more further header bar elements, the fixed header bar section supporting at the first end a first pillar extending generally perpendicular to the fixed header bar section and via which the first moveable wing is retained moveably captive relative to the fixed header bar section. The first moveable wing is moveable relative to the first pillar vertically and rotatably from an operative, deployed position in which it extends generally parallel to the fixed header bar section to a stowed position through vertical movement on the first pillar and rotation such that the first moveable wing lies adjacent the fixed header bar section inboard of the first pillar.
