So I've had a good look at your pictures and had a look at the fitting of Lynne's changer that I fitted not that long ago .
So
This piece of cable is not factory as far as i can see ( could be live
)
This plug here
I can't see in your picture but should be a red with white tracer and a brown This is the power cable joins the yellow and black cable with white plug out the changer
This appears to be exactly what it looks like.
A piece of co-ax.
This is either from your original aerial or an aftermarket add on ( if an add on there may be 2 co-ax cable behind radio mount.
That's the easy bit over now for the more complicated stuff.
This is the data cable from the front obviously cut
that is the cable in the background don't know if the yellow writing or numbers will match the bit you have in car anyway there should be a big plug on the end that plugs into corresponding socket on cd changer
There is only 3 solutions to this issue
1. You fit a replacement cable all the way from front to the rear .
2. Get a piece of the cable with the plug from the car side of loom (
@spurs fan in a coupe may be able to help)
Then join the 2 bits together ( a fiddly but not impossible task) that will give you the plug end to plug into the changer cable end.
3. Cut the plug off the new changer and join to broken piece on loom
Option 1 most work best results.
Option 2 less working more fiddly soldering all the little wires.
Option 3 last resort as ruin the changer resale value if you cut off the plug .
Stephen.