Slitherine

p.63 under "Retiring Units" says, 'Units making a retire or an evade move go directly away from the enemy causing them to retreat." Also there's a written in clarification that says, "The direction of a retire when in contact is in the direction faced by the enemy unit causing the outcome move...".

Does this mean units retiring or evading when not in contact, go directly to their own rear, as against in the direction faced by the enemy?

yes...to table rear

If you are forced to retire by shooting or evading a charge, you use the path of the shooting or the charge to determine the retire or evade direction. Easiest way I find is to turn the affected unit to face the unit or units that are forcing the move then move backwards using your units new rear edge for measuring.

In all cases of outcome moves by shooting or evading a charge it is the direction the enemy is facing/moving/shooting that will determine the path of the target unit. Not the target units own facing. You can force an enemy unit back into its own lines and cause burst through and cohesion drops.