It might not be quite what you are after, but did you now that you can camp on Dartmoor. I was down there in August and picked up a local tourist guide and wild camping is welcome - but obviously no fires.
I live 5 mins from there by car, and then a short hike LOL
I've heard the caves are stunning but you wouldn't find me following you down there LOL I wouldn't even camp up top, tho I'd love to. In summer, the weather can change so fast it's unbelievable! We parked up there in August to watch meteors and by 11.30pm we had to leave as it got freezing, despite our being well-prepared, Little-un's teeth were chattering. Rumour has it that the army have lost people up there My uncle went up there to walk the dog and when he didn't come home by tea time they had the helicopter out to find him - expensive walk that!
Most remote place I've camped, a farm field in cornwall, there was no toilet, no water and we were miles from the farmhouse - not sure it counts tho :D
------------- Life is what happens when you've made other plans