We love Caerfai Farm near St Davids in Pembrokeshire. Lovely spot with fantastic views - great for kids as above a really safe beach. The area in the middle of the camping fields is kept clear so there are always impromptu games of cricket and football going on with the kids from the site. Dogs allowed too.
For something a bit wilder, then it's hard to beat Mynydd Mawr on the Llyn peninsular near Aberdaron. Facilities very basic, but again, stunning views out over Bardsey Island and a real back of beyond feel.
We've also stayed here a number of times: http://www.graigwen.co.uk/modx-0961p2/index.php
The camping area down near the estuary is stunning. Direct access onto the Mawddach trail and handy for CyB.
In Cornwall, I really rate Henry's on the Lizard: http://www.henryscampsite.co.uk/ ... a bit hippy dippy, but good fun, and again great for kids. Some great walking thereabouts as well.
Although it's v expensive, I also like Tristram campsite at Polzeath. You can't beat it for views / location / easy access to the surf etc, but it does get very busy - probably best left for out of season.
Not stayed at Pool Bridge, but it gets very good reports. Nearby there is also Burrowhayes Farm - http://www.porlock.co.uk/members/index.php?id=00073 much bigger, more commercial site, but has some of the best facilities of any campsite I've stayed in, and direct access onto Exmoor. Very friendly too.