Many thanks to Garm for providing the confirmation on the location and the other information - I thought it could be Branksome Chine but my visits there have been on gloriously sunny days which are rather at odds with the picture! I have some picture of it still in the camera - I will try and scan them in when I have got them developed or borrow a digital.
I didn't go to Oxonmoot last year and so missed it (though the art room isn't my usual haunt) .