Welcome to Susanna via Bloglovin. I have put a link here which takes you to the British Clematis Society web site on how and when to prune clematis.
The one I have growing over the oil tank is Clematis "Macropetala Wesselton" a Category 1 requiring no pruning unless necessary:
To the right of the front window are two plants,. The first is Clematis "Veronica's Choice" - a Category 2 requiring a light prune back to healthy shoots in February. It can be pruned again after flowering to produce new shoots and flowers. This is a strange clematis as it has double flowers early, followed by single flowers later on:
The one growing to the left of the front window is this one: