I've had this noise when the engine is warmed up and at idle since owning it, and it hasn't gotten any worse in the 5-6k miles I've done, but it is pretty irritating with the windows down. I haven't held back with the loud pedal either, so I would have thought if it were a bearing, by now it would have said sod it and er ceased being a bearing...
Thumped the cats - they don't seem to make a noise. From the top side with the bonnet up you can't really hear it - but you can from underneath and the sides. Soon as the revs get over 1000-1200 its gone. I don't get any knocking under load or any other unwelcome nasty sounds.
Soon as I noticed the noise back shortly after getting it, I had the sump off and gave things a wiggle - no up/down movement in any big ends, a tiny bit of lateral play.
The tinnier bit of the sound makes me think its something relatively lightweight clattering somewhere, but I've yet to work it out. Sounds about the same from both sides.