I've found SARD wondersoap great for stains, Mel. worth a try. I usually rub it on and leave to soak in for a bit and then come and rub some more to remove the stain.
I've also heard that if you leave white things on the line overnight it can help whiten them, not sure about removing the stain but worth a try
(but that could have just been some bull that some one fed me and I believed it so it would be ok to leave clothes on the line overnight
)