When I had the seats up yesterday to take piccies, I also (i think) identified the source of my high pitched squealing, which can be heard from the cab. Alternator Belts. As demonstrated in this video which I took at the time!
http://www.youtube.com/watch?v=D_FOTc4kUYo
http://www.youtube.com/watch?v=viHLd9uibXg
http://www.youtube.com/watch?v=llwyjBFFXtk
Battery was reading at 13.2v so it's not getting discharged, just a small slip, but I'll see about tightening it up when working through my list of things on Friday (hurrah for a days holiday!).
I'm assuming there's a fact-sheet or set of posts from members on here. Will have a search later today

Cheers,
G.