A unit that has been joined by a character moves as normal, the character model moving as part of the unit. A character model that is positioned adjacent to the unit must remain adjacent to, and in base contact with, the front rank of the unit at the end of its movement.
A unit that has been joined by a character always uses the Movement characteristic of the slowest model. If either is subject to any movement restrictions, these apply to both. For example, if a unit with M8 is joined by a character with M4, the unit can only move 4".