thanks for your reply. i cant get any pics of my trunk space as the car is not currently with me but i have pics of the cable below and descriptions of what i have managed to do so far. hope this is of some use in understanding my current config

here is an image of the cable


these 2 are connected to the back of the sat nav


this is going to the back of the TV tuner


this one is connected to the onboard monitor loom and seems to provide muting etc. there is one wire on the connector which is not hooked to anything and is purple with a red stripe


this one is unconnected as there is noting to connect it too. i believe this is the reverse and speed sensor.
the 3 wires are
white with yellow stripe
yellow with white stripe
yelow with red stripe


this is the final connection and i have no idea what it does.it is located midway along the loom and has the following wires that i can see
blue with white stripe
blue with yellow stripe
green with white stripe
green with grey stripe
brown with black stripe
red with green stripe
purple with red stripe