Hello TooTicky I noticed the other day that Getknitted have started selling something called Ecowool, and I thought of you! Don't know how it reflects on animal treatment, though. it's here. Cascade 220 is a wonderful wool yarn from there too, and is actually reasonably priced considering you get 220 m for the money. Agree with Pruni, Jannette on eBay is wonderful. Texere is also worth a look, they have some real bargains.
I can't remember how far you are from Bradford on Avon, but there is a shop there that mainly sells cards and stationery, that kind of stuff (called Quire, something like that?- near Bishopston Trading, anyway) and the woman who owns it has sheep and sells their wool which she gets spun for her locally. It's all aran weight in natural colours, I think about £3 a ball.