One recent approach- which I personally don't like- is to give no pruning advice at all. Many of the Raymond Evison introductions give no clues at all to pruning. I guess the idea is that the information would frighten people?

I completely trust the information given for clematis on the Hull database site. They will tell you if a vine can be pruned in more than one way for best effect.

http://www.clematis.hull.ac.uk/clemdetail.cfm?dbkey=593
http://www.clematis.hull.ac.uk/clemdetail.cfm?dbkey=329

Pruning is not law. There are various ways of treating a plant for different purposes. For example one person might want blooms to cover the feet of a rose bush, while another would use the same clematis to cover an outbuilding or to only have blooms high above a pergola. There's plenty of room for experimenting!

Warsaw Nike I have never seen listed as a type 2; I am fairly certain it's a type 3, and behaves fine like that in my garden.

Mrs. C I know of as a type 2, and treat her this way, but I think I've also seen her as a type 3 somewhere, you're right. I agree with Gardenbug, though, to trust the Hull Database (where she's listed as a 2).

Other larger, light-blue options for your pairing that are all type 3's would include:

Victoria
Blue Angel (but bleaches easily in full sun)
Perle d'Azur (a real winner!)

...none flower quite as large as Mrs. C, though.

Even smaller light blue type 3's:

Emilia Plater
Prince Charles

Some clematis can be grown and pruned as a group 2 OR as a group 3. This means that the plants can bloom on 'old' wood as well as on 'new' wood. Mrs. Chumley (Mrs. Cholmondeley) is one such clematis which falls into this 2/3 group, however it doesn't mean that all group 2's can be treated as hard prune types, either! I wish that the growers would let the consumers know this, but it can be a bit confusing for them to explain to consumers, so they simply don't. Sometimes, I think that the growers themselves are a bit confused!

Warsaw Nike has always been a group 3, heavy prune type, as Michael stated.

A Mrs. Cholmondeley which has been heavily pruned will bloom later in the season than if you treated it as a group 2.
Suzy

My Mrs Cholmondley was chopped right back in about June due to wilt and she still managed to crawl back and bloom just now. It's not the most luciously thick plant (one stem) but it is her first year and in spite of the wilt. So hard pruning her really doesn't do any harm at all.

{{gwi:618013}}

It can be frustrating but some of them fall into a category all of their own. One website calls it a pruning B2 method. That's either pruning as a group 2 or as a group 3 because they grow on BOTH old and new wood. You are doing the right thing by asking other people here.
Good luck with your growing.

I do not know a thing about clematis at all and one year I cut it to nothing and it came back with a vengance. LOL. I am here researching what i am supposed to actually do. It was taking over another plant nearby, so I had to rescue it.