firefox wrote:
Had to call the experts out - he was quite a long time trying to get it
clear.In the pipe was chunks of limescale , some of them huge.
Getting up on roof would be very difficlut due to conservatory in the
way, but I did think of it.
Thanks for all your suggestions.

Told you to use sulphuric acid didn't I? :-)

Gets rid of limescale fast that does.