Thank you everyone, that was fairly unanimous
So, I just phoned the supplier and they have said to send it back, to a freepost address, and they will refund. I think I will send a specimen of the stuff I already have as a benchmark of what I was expecting. I got the expected 'it's a natural product so it will vary with each animal', but as far as I'm concerned this is outside the acceptable variation.
Now I'm too disenchanted to buy more by post, so it looks as if the yarn I'm spinning will be all oatmeal

Maybe I will dye one singles...........
This was one of the major suppliers, so I'm surprised to have been sent poor quality fibre, but perhaps they ran out of the good stuff at Woolfest. Of course I should just have bought this second lot there too, but I couldn't make up my mind - she who hesitates is lost

What a dingbat I am