you're not supposed to camp anywhere unless you pay, or you get permission. although it can be done in remote places such as the dorset coast path or welsh mountain areas. or as you say , maybe in the woods. be quiet, be tidy. dont do any damage and you may be ok if no one sees you. ive camped on the dorset coast path in a tiny tent and left early next morning and ive seen others do it.
theres no freedom left in this country. all you can do is be discreet and hope you get away with it. its a sad place we live in now but good luck with your camping. i hope you enjoy it