Aha...
Thanks GG those were helpful links. It looks as if it will need a new bit of wire and what are the chances of BT doing that??? The numbers indicate that I'm right on the limit between 512k and 1 Mb which is sort of borne out by the fact that at some times of day I can get better speeds that at other times. However it still comes down to getting BT and my ISP to stop blaming each other and cooperate to improve the service. I think I just caught sight of a pink pig doing a barrel roll past the study window. Unless anyone else wants to add to this I'm content to call a halt to this thread. I've bookmarked the links so thanks again to all.
The Ancient Mariner