Hi Dave,
Open up the panel (for fuse access) under the glovebox and have a look for a connector that looks like this:
A few months ago, I retrofitted a glovebox CD changer to a Club saloon and that didn't have the wiring in place. Fortunately, the 2nd hand changer I bought came with some of the wiring (in the photo above). I bought a blue mini ISO connector off eBay (interface with the Symphony stereo) and adapted the wiring to fit as it was off a car with the Harmony stereo which has a different connector I believe.
https://www.ebay.co.uk/itm/185818505...mis&media=COPY
The CD changer also has a K-Bus connection which I wired into the factory position here:
Hope this helps