Elsie G. Davenport's Your Handweaving (Tarzana, CA: Select Books, 1948), p. 26 suggests for weft "fleece gathered from the hedges, washed and twisted slightly to strands about as thick as the cotton rug yarn."
Margaret Hutchings' Teddy Bears and How to Make Them (New York: Dover, 1964), p. 65 refers to gleanings in the section on stuffing with sheep's wool: "Country women can often collect this material off hedges and barbed wire fences. Carefully washed it makes a wonderful toy filling."
Davenport and Hutchings were both from the U.K.
The Guardian has a slideshow with narration on how to make a classic fleece-snagging English hedge: "Disappearing Acts: Laying a Hedge," March 31, 2010, http://www.guardian.co.uk/money/audioslideshow/2010/mar/22/laying-a-hedge.