I have to say that NONE of these sites would get my vote, and the reason is connected to Alan's comment ref. the Start Bay site. Depending on the size of your van, many of the Devon and Cornwall sites (and we used to live there), have VERY narrow lanes leading to them. Forget about dual carriageways with nice wide sweeping drives into the sites, we are talking lanes here!
The fact that YOU are towing a caravan will not give you any kind of leeway on such lanes, and if you meet something coming the other way, and it could be another caravan or an agricultural vehicle with a LONG trailer, then it can lead to some interesting communication situations!!
This is something that is rarely, if ever, pointed out in the sites publicity. Getting to some of these remote sites can be a horrendous experience, especially if you have a new or well turned out caravan. Trying to negotiate a caravan down a country lane built for a solo car or a tractor with sharp blackthorn scraping your nice shiny acrylic windows is not for the faint hearted!!
Try this site for listings of other sites, many of which have far more accessible and better sites.
http://www.caravancampingsites.co.uk/
I would ALWAYS check out the access to ANY site (certainly in the UK), before even thinking about a booking. Caravans are expensive, and damaging your caravan or motorhome before you even get to your destination would be a not very nice way of starting your break.
For us, good access straight off an "A" class or WIDE "B" class road, is essential, and well worth checking out BEFORE you make your decision.
If you DO decide to go the "lanes" route, then NEVER, EVER, reverse your caravan in such a lane, unless you have a family member walking behind the caravan to check clearances at the sides, back and even above your caravan.
As I've said, we lived in Devon for many years, towing our caravans all over Devon, Dorset and Cornwall as well as further afield. Narrow lanes are bad news. Take it from those that have been there and done it!!