Dogs in motorhomes

Hi All

Need a little advice from all you seasoned tourers. I am thinking of getting a motorhome as I like to visit stately homes. I have a border collie that comes everywhere with me but I am concerned about leaving her in the van. How do you keep your dogs cool when locked in the van. She will be in a crate as she suffers from seperation anxiety and is happier when crated ( large pink affair with single bed duvet so very comfy )

Lynn