A short distance north of the Grassington/Threshfields road junction in the direction of Kettlewell a small lane goes off westwards. This is Skirethorns Lane. There is a camp site at the start of this lane but it is mainly residential caravans and family campers (Wood Nook). However, the owner (at the farm opposite) used to allow camping in a field further up the lane (In fact, a lot further up the lane). This is (or was, the last time I used it with a group of kids)just a field, no loos or washing facilities, and a bowser for fresh water.
Bell Bank House,
He may offer useful advice.