Only certain ones need pruning like that. The simple rule is Flowers before June, don't prune.
However there are 3 pruning groups for them.
1.Prune only if space is limited. Spring flowering ones like C.alpina.
2. Cut out dead growth, shorten all stems back to strong buds.February-March Large flowered types like Nelly Moser.
3.Cut to about 1 metre or lower in February .C. viticella etc.
Most sold ones have a letter or a number indicating to which group they belong.

Thank you Owdboggy 😊 The majority have already flowered or are in flower now, I ask because the bottom part of most is all stem and no leaves then all the leaves are at the top and I’m trying to get some to trail across my fence and entwine around a wagon wheel. I shall have a look for the letter or number in the future.

If you know the name then we can tell you which group the clematis is in.

I think one of them is an alpina it is blue and has white fluffy seed heads on it which has finished flowering now the others I think are:

Amethyst beauty
Niobe
Montana

Amethyst Beauty Reduce all stems down to 6" (15cm) late winter/early Spring.
Niobe remove any dead or weak stems in late winter or early spring and cut remaining stems back to the highest pair of strong-growing buds.
Montana remove dead or dying otherwise no pruning.
alpina ditto

Oh wow thank you so much 😊 I was so worried about caring for them properly, I really appreciate the help.

We had over 100 Clematis is our previous garden. None here, they just will not grow. Too acid a soil, they prefer alkaline.

Wow that’s a lot, My mum had me count hers once and you wouldn’t think it to look at her garden but she had over 40 at one point and I thought that was lots lol.
Oh no that’s sad that you don’t have any now, they make lovely features as well as it’s beauty as a plant, I think.
I will have to remember that about them not liking acidic soil, thank you Owdboggy 😊