Heritage Coast - Vale of Glamorgan, Mount Folly Farm - Bigbury On Sea, Porth Joke - nr Newquay. All allow campfires, although Porth Joke you need to take own fire brazier, fire must be off ground. All within walking distance of a beach. Heritage Coast's booking page says it is closed but it isn't just contact them. Hope that helps!
Ooh thanks! hz is it you that has the camping blog? I saw it linked to on another page, called Yellowfields I think? Fantastic blog! It reminded me of what I love about camping, and just hanging around in nature with the kids!
Have a look at campsite UK and use the map search, and also the campfire search, and the beach search.
Nearish the sea and allowing fires, if E Sussex is OK for you, look at Alfriston Camping, or Hawbush Farm, (eastbourne direction, I think) or Nr Hastings - Freshwinds, or in Dorset Riverside Lakes or Longthorns Farm?