Group 3 Clematis pruning

Is it too late to prune my Clematis Viticella Polish Spirit?  Watching last night's Gardener's World programme made me think about Clematic Viticella.  I have so many clematis in my garden as I have a passion for them but I was then prompted to see if I had any viticellas and I have one which is Polish Spirit.  I haven't pruned it yet and it is putting out lots of buds.  I should have cut it right back to the ground during the winter or last month but as I did not do this, is it now too late at the end of March?

We have a Montana which has climbed up a tree and must be about 20 - 25 ft tall.  I have never had any advice on it.  It flowers beautifully every year and dies off in winter only to flower beautifully again in the Spring.

viticella wiil bloom later if pruned now-montana should be pruned if at all after it blooms you can cut the oldest growth at the base and just pull it out-too severe whacking frequently kills it

Thanks for your advice and help.

I caught the Clematis bug last night and rushed out today, buying 3:

Sunset (Gp2) - flowering May to Sep (according to the label)

Hagley Hybrid (Gp3) - Jun to Aug

Pink Champagne (Gp2) - May to Aug

Each are 2-3 foot tall, several stems which start a bit woody (albeit very thin) and go on to new green growth and are well leaved, none are begining to flower.

Should I prune them back at the time of planting out (as stated last night) or wait till after this years flowering /next early spring?