Thanks Tiompan for your response, I did think of Lindow Man and yes I agree, the practice of suttee is well documented throughout history.
Thanks also Littlestone for your very comprehensive and very interesting reply about the folk-lore surrounding John Barleycorn - and the link (I was quite startled when my lap-top suddenly burst into folk music).
The Tony Grist poem speaks specifically of the sacrifice of a four year old female child and it was really that such practice I was asking about. I do admit that the twentieth century mother in me recoiled but my interest in anthropology (especially concerning the peoples of Britain) wanted to know more. A bit like "did they they really send children up chimneys and down mines in the 19th century". Another thread perhaps?