Need some advice on a head unit, when I got the car (56 toran tdi 2.0) the old owner said you have to pull the face plate off or the battery will go dead, I suspected it just to be a swap of the red and yellow cables and job done but..... Haveing don't this the same issue has arisen, is this just a nother vw gimic and power has to be sourced from say the fag lighter, or is there something else that needs changing 

Hi....welcome to the Forum

Usually there is a combination of red and yellow wires which can be swapped around to retain the memory in the head unit.

This should not necessarily discharge the battery as the current drawer is minimal.
I would look at other sources for the current drain