Hmmm, sounds like Clematis wilt assuming its not too dry at the roots. It may well not be the end for the Clematis plant, but it sounds like it for the flowers this year.

If the whole plant dies back, lift it with a good rootball and replant 4-6ins deeper than it is currently (assuming its not in a container).

Cut it back to base, too, and get rid of the dead stems. When mine die off from wilt - one of them does it every year - I get new shoots from the base in spring, and off we go again. If you did plant it deeply to start with (in the ground) then you shouldn't need to replant it -only if it was planted at ground level (or in a pot)...

I will take on board all your advice, and keep my fingers crossed for next year. Many thanks . Noodle. x

Good luck with it - I know how frustrating it is!