It's a version of "The Unquiet Grave", innit?

BTW the first tune for that in Mudcat seems to be a variant of "Westron wynde", which might be one of the oldest English tunes known.

I first heard "I Am Stretched on Your Grave" in a rather pub-rockified version by a local singer - it gets around. Made more sense to me when I heard the Dead can Dance version.