X5 E53 missing audio components?

[Yetster]

Hi everybody,
I've just bought a 2005 E53 X5 3.0D Sport.

All good so far, but I have no sound from my high sat nav / radio. The navigation works fine, I have upgraded to v32 with 2017 maps, just no sound.

It looks like the 6 disc changer has been removed and the wires cut, I've bought a new changer and a piece of cable with the connectors so that I can wire it in, but I'm not sure what else may be missing to cause the lack of sound.

There is also another wire that had been cut, looks like thick speaker cable, but I'm not sure.

I have an iPod cable that was wired in my glovebox, and when I push the radio button this is the only source found, so I guess that this is plugged into the aux instead of the changer.

I haven't looked under the dome yet to see what else may be wrong, but I'm not seeing an amp, should there be one?

Pics attached.

Thanks for any help or guidance