VDO CD 413 downgrade to older Rover units

[grteam]

Hello all ICE connoisseurs. I have a March 2005 MKII new to me, must be mentioned I come from a 2002 Connie SE with Highline Satnav TV setup, proper stuff. To me it worked fine, never fancied so much the state of the art ICE units are trending now, I love those cars for what they were intended to be. Just love them, sir.
So now I ended up with a resonably nice and low mileage MKII CDTi that brings happy times to me and my 100% 75 fan family. All of a sudden I am no longer able to stick in my old fashioned cassette adapter, as the OEM HU is an utterly misplaced VDO 413 CD player unit. Works fine, Parrot included, but I can't hook my most advanced electronic device, a Samsung feature phone, and listen to my miriads of selected relaxing tunes. I have an offer to swap it with a Harmony, which would be fine, yet I might need adapters from ISO to Quadlock or what is it called, that I understand the Harmony and Symphony have. Any input would be more than welcome for following questions:
-What type of connectors do Harmony and Symphony have? I have here ISO connectors, and steering controls work, will they work without any mod with above HUs? (able to understand re-wiring, so I am not put off).
- In the unlikely event I keep the OEM VDO, has anybody experience with the 3.5 mm jack adapters at this type of old CD player? does it actually have a CD changer port (not being able to find out from different sources, but I think not, so I do not see how will it see as ''CD changer" the device at the other end).
If someone will ask why down grade, please consider beauty is in the eye of the beholder, I like better the old fashioned colour matching (with airco controls) buttons. Sorry for long post. Thanks in advance

Edit: what way would you go in order to have 3.5 mm jack conectivity? Not refusing other aproaches actually, but not willing to spend much as other points need attention. Cheers