At championship shows where you have benches for the dogs, each breed has a minimum size. This is supposedly enough room for the dogs (I will let you decide!) And the benches for your breed should never be smaller than this.
If you get to a show and find they are smaller and you feel it’s too small, my advise would be to go a show official and speak to them about it to help resolve.
The below lists were found on the Kennel Club website back in 2012. But I doubt much had changed. I hope this is useful for deciding on cage sizes etc
