@Corjan-Meijerink Out with my partner yesterday in the car, she was driving, I tried again and voice instructions worked perfectly for the entire route. It even mentioned a landmark educational establishment in one of the turn instructions, this was passed after the turn. Particularly impressed with that.
If I had managed more on-bike experimentation I would be considering removing my Garmin and just rely on the phone for this week's trip to Germany... Alas, that's not the case as work and life have prevented that.