Thanks Bob. I bit the bullet and bought a new Outlander head unit from a wreckers. Got the GPS antenna (I think the plug is slightly different), and the 2 USB cables all the way from the input plugs. At first install the things that work are radio, USB, Apple carplay including maps (love it, main reason I wanted it), steering controls, I'm sure DAB will work with an antenna. Bluetooth connects but no audio yet, and microphone isn't connected as expected. My factory reverse camera isn't working, oddly the plugs are the same but the new unit only uses 6 wires compared to 8 on the old unit (I have all the plugs from the outlander to compare).
I'm sure I can solve those issues without too much drama, but it's throwing out the dash instruments. Revs, 4x4 indicator, engine temp, illumination etc all flashing or behaving oddly. The outlander unit has engine info displays, which of course aren't working (and I don't mind if they don't, didn't expect them too). I'm hunting for a wiring diagram of the new unit to compare to the old.