Rillo - huge thanks. I tried a newer iPod version as you recommended and the problem is solved. Major irritant removed.
I am now adapting to the slightly harsh suspension, albeit less so to a trim rattle somewhere around the rear seats. At least my iPod now drowns it out! Hopefully the dealer can resolve when the car is next in.
In any event, passengers praise cabin comfort levels to the skies, so perhaps I am over-sensitive to some of these things.