Caravanning with collies

Can anyone recommend any truly dog-friendly caravan sites? We have a touring caravan because we always take our dogs on holiday with us, and are looking for sites that have dog walking facilities on site, or immediately adjacent, that enable our dogs to run off-lead. We have three Border Collies who need some free-running time before we set off for a day's exploring. We would prefer electric hook-up and ideally an adult only site, although we do take most of our holidays out of school holiday time so it wouldn't be a major issue.
Susan Webb, by email

My earliest memories are from under canvas, camping with my parents and, at that time, our Border Collie cross Pedro. Over the years, we gathered more Border Collies until we were taking six away camping with us, so I know exactly what you are seeking.
As a camper, I have long been a member of the Camping and Caravanning Club whose site book gives detailed information such as the availability of dog walks on and near a site. There is also the website, and contact information is usually listed so that you could always ask before booking. There is also the Caravan Club which I would imagine provides similar information.
Alison Logan, vet