Ukcampsite.co.uk is a great website because it allows you to search by your chosen criteria and then read loads of independent reviews about possible sites/
Here's the search page for Dorset:
http://www.ukcampsite.co.uk/sites/results_adv. asp?region=South%20West&county=Dorset
Set 'Statics to Hire' to 'Yes'
Also choose 'Yes' for 'Tent pitches and/or 'Motor caravan pitches' and/or 'Caravan Pitches', depending upon the type of camping your friends intend doing.
Set any additional options to 'Yes' depending upon your preferences.
Click 'Search'.
When you get the results you'll probably find it easiest to
right-click on the links, so that you can open them in new tabs (or windows). It makes comparisons easier.
The links to reviews can either be accessed from the results page or from the pages for specific site details. (They're rather hidden on those pages, at the top of each page, just below the address).
Here's the search page for South Devon:
http://www.ukcampsite.co.uk/sites/results_adv. asp?region=South%20West&county=S%20Devon
and for North Devon:
http://www.ukcampsite.co.uk/sites/results_adv. asp?region=South%20West&county=N%20Devon
Chris