Looks like H. F. Young to me - petals vary between 6,7 or 8, but the stamens are always this pale straw colour

Thank you again Bamboo. The name doesn't ring a bell but I must have bought it!! It certainly looks like it on Taylor's website. I was looking at mauve colours rather than pale blue. It is positioned next to a John Paul II which I thought was a white/ cream but is pale pink when it's bloomed for the first time this year. I hope it fades a bit with the sun and they compliment each other. Thanks again

Also known as clematis lasurstern, often listed separately as well as H F Young, but the RHS lists the names as interchangeable. I can't see a difference between them, but maybe you bought it as lasurstern and not HF Young, Taylor's has it listed.