Perhaps this article can help:
http://en.wikipedia.org/wiki/Patterdale_Terrier

If a black terrier is rough coated, rather than smooth, it may be called a Patterdale terrier, but it is more commonly called a "fell terrier" while a rough-coated black and tan terrier may be called a "fell terrier," a "Patterdale terrier," a "working Lakeland terrier," or a "black and tan terrier" In the world of non-Kennel Club working terriers, the only real proctor is the quarry itself