Edinburgh,
United Kingdom 
I am in exactly the same position as Shadydappler with my clematis rouge cardinal (group 3), I only pruned it a little, about mid Feb, leaving a few feet of old wood, and on this lots of new growth has sprouted. Unlike Shadydappler, I bought the clematis new last spring, so have never had to decide when to prune or how far down. It seems a shame to take it back to 6-8" now, as I like the form it has on the wall, however will it not flower if I leave it ... must I prune it hard now to guarantee flowering? thanks, Vg
13 Mar, 2011
Answers
You'll end up with all the flowers way up above the height where you can enjoy them! Group 3s need to be pruned hard or they go romping away. They still flower of course. No clematis 'has' to be pruned, you can leave them well alone, but you end up with all the flowers out of reach and nothing but bare stems in view! Go for it! Here's the BBC advice....I don't think it's too late, certainly not up here in the North, where they are only just beginning to show growth at the bases. Have fun and enjoy your clematis...I do!! ;)) http://www.bbc.co.uk/gardening/plants/plant_finder/plant_pages/7147.shtml
13 Mar, 2011
I answered this query under Shadydappler's original question, Virgingardener.
13 Mar, 2011