Stu, thanks for the info about Heck Fold.
I'll go and have a look and see if I can identify which building it might have been.
Though I am "local"' I've never come across the word heck meaning mistal or cowshed. Very interesting-wonder what the origins of the word are? I know that mistal/mistle comes from the German word Mist meaning, politely, farmyard manure! Quite a lot of houses around here, converted from old barns, have been named "The Mistal", presumably by owners who are unaware that it originally meant cow(ie manure)shed.