After getting completely pissed off with sites that charge per tent/person/awning/pup tent/dog ect,pack you in like sardines and have lists of rules an arm long,I have done some research and booked 5 days in Cornwall and 4 in Devon for £10 a night for a all of us.Myself H and D.
They are basic semi wild type of places with camp fires and errr "interesting toilets". One even has a hot tub (if you light a fire under it 
Simple,natural with loads of space for D to explore - I can't wait!