hi pignut,
In my opinion, a black fell, is a terrier with a rough / broken coat and a patterdale a smooth coated type ie: gould lines and nuttal line.
Many people will argue that because the town of patterdale is in the north lakes, that the terriers from that area, should be mostly rough coated, due to weather conditions etc,, thats why people think rough coated black terriers should be called patterdales.
Most fell terriers are rough coated, lakelands, black, black & tans, and most terrierman have breed between all the strains of fell terriers, and even breed from predigree k