So, last week I suddenly noticed some distortion coming through the sound system (B&O). Tracked it down to the centre driver's door speaker, which is distorting badly at moderate to high volumes.
Car is booked in to the dealer tomorrow so we'll see what they say. The only thing which springs to mind is that the inside of the door did get quite wet the other week when I was loading up the car in the rain. I did wipe the excess water off but can't for the life of be believe that this caused the problem. If they do turn round and say it's due to water ingress, and thus possibly not covered under warranty etc, then I shall blow a gasket as cars should be designed with the inside of doors getting rained on in mind! But I'm getting ahead of myself here. Will report back with what happens tomorrow but am a bit miffed that a speaker has failed so soon on an optional £700 sound system, if indeed it is just a random failure.