No idea on the nappy library front but Fill Your Pants do a 'Try Cloth for £10' scheme which I've heard good things about: http://www.fill-your-pants.com/cloth-na ... trial.html
Or you could buy a few pockets/AIOs preloved on the Classifieds and see how you get on?
Personally, I love prefolds on newborns. They are soft, dry quickly and offer great containment when teamed with a decent wrap (e.g., Thirsties Duo). We used them with DD2 until she was chunky enough to fit into our OS pockets without leg gape (which was around 12lbs for us). I'm completely the opposite to the previous poster in that I've found pockets and AI2s great on my girls - even when they were exclusively
. So it really is worth trying a few different things out once Bubs is here. You might be surprised by what you love/works for you.