Rainyday, I was in the same position last summer. I dug my 'Proteus' and divided it in the middle of summer with no ill effects, all three pieces were replanted and are doing well. I see you are zone 8 do you have a mild winter, if not I'd wait till spring.

Annette

Here is a link that might be useful: Moving a mature Clematis

I replied to aftermidnight via email. Thank you.

I think I will go ahead and move it now, as it is a very hardy plant.