Where there is a choice of foes to flee from, warriors will always be more determined to avoid the most numerous enemy. The controlling player decides the order in which units flee.
Each fleeing unit pivots about its centre (ignoring enemy units) so that it is facing directly away from the enemy with the most ranks of five or more models (select a unit randomly if there is a tie). It then flees straight forward in this direction as described earlier.
You may find that this involves the fleeing unit turning so that it overlaps one or more other units in the fight. If this happens, don't worry. Simply estimate the unit's new position as best you can by holding it above the rest of the units in the fight – it'll only be there for a moment before making its flee move, after all!