In reply to MikeMarcus:
My information is 10 years old from when I used to live in the valley.
Low wood is owned by the national trust and there is a NT office on the edge of the wood, so staff around who will tell you to move on if they see you.
However if I wanted to I would bivvy/camp there for 1 night but would pitch up late, pack up early in the morning and leave no trace.
Having a camp up during the day or leaving any trace would not be on in my opinion and would quite likely be spotted. If you want to stay more than one night use the NT campsite at wasdale head, the nice site at Santon bridge right next to the pub, or the cheaper more basic site near the wasdale head Inn. All those sites are less than 4 miles from low wood.