Somebody must have voted, as this thread has been bumped. I somehow misse this thread, but I see no harm in taking hanging branches that have snapped off higher up and are caught in lower branches. If you see forestry work going on and they leave loads of freshly trimmed branches, take some and use them. Maybe even stick some up a tree out of the way for next time. If they are off a main path, they won't be disturbed.
Saying that, the last few times I've been out, I have done what Wayland has been doing for years. No, not growing my hair, but using pinecones. This is a much under estimated resource, once they have done their job of scattering seeds, they make really good fuel. If you get the typical pine cone with thick tines or whatever they are called, they burn good and hot, will boil your billy in no time and are in vast numbers on the forest floors.
Don't use the long banana type pine cones, they are always wet and don't burn very well at all. This is one reason I never tried to use pine cones before, kids chucked one on the fire and nearly smoked me out. Wayland made a two minute camp cooker at Delamere from an old cooking oil drum, filled it with pine cones and cooked pork and apple sausages for us, they were wrapped in those tortilla thingies, and tasted great! All thanks to the humble pine cone.