Only comment I have to make is regarding replacing the SatNav unit ... rather than using another Volvo C1-series unit, could you just replace the entire CD player / radio / etc with something that can interface with a 'phone & use the in-car screen, ie. Apple CarPlay & Android Auto. That way you can always switch between SatNav systems (some free ones are very good & in fact a lot better than what's in many cars), you can always get the latest maps, etc.
How long do you have to wait, and how long does it
feel ...
