Clematis Pruning Group 3 Quandary?

I normally prune my group 3 clematis down to half a metre in early March. Now we have a caravan in the Morecambe bay area with two very nice clematis. I can only access the site from April 12th.
Is it OK to prune back then and see what comes, or should I leave it be?
Can you prune back group 3s at the end of the season, say mid November?

TIA

 

This type flower on wood produced during the year which is why they are pruned in early Spring. That encourages new growth from low down so that the flowers are visible rather than all at the top f the plant. That being the case, then you may prune in November when the flowers are finished. BUT That does mean you may have to re-prune to remove any dead material again in Spring.

 

Thanks @Palustris I'll cut them back next week, otherwise all flowers will be at the top of the plant.