Here are some photos of what you can do with ivy berries. Many of us have only managed to dye a pinky grey with ivy, but Rosie has obtained a wonderful milk chocolate colour. The picture really doesn't do it justice. The secret, apparently, is to leave the ivy berries to soak for several days, and then mash and strain - and leave the vat again - before dyeing the yarn. The lighter colour was obtained without a mordant; the darker colour with alum and then iron as a modifier. The yarn is "coloured" Corriedale, but, take it from me, the fleece is barely off-white - certainly not this brown!
So, now we are all rushing off to have a go ourselves. I have posted some preliminary photos on the Web Album