Posted: 09/06/2013 at 15:48
Sorry, I somehow missed the fact that you gave the names your first post (it's what comes of nipping in from gardening for a few minutes for a cup of tea!) Nevertheless, they are indeed Group 2 so can be treated as I advised. You would only cut them back to 30cm in their first year, to help develop more stems from the base, unless you were indeed growing them in containers. Here are your clematis on (the best, in my opinion) clematis site on the web:
Ooh La La:
The first two will reach 1.5-2m, but Ooh La La will reach 1m max, according to the Hull university site above.
As others have said, probably best to consider a mix of climbers if you want the whole trellis covered. I grow a few Winter-flowering evergreen Clematis Cirrosa "Freckles" which can lightly cover a large area, have small pretty leaves and are easy to control/look after (just cut off any stems growing where you don't want them - simple!) I grow Group 2's through them.