In reply to snoop6060: its right below the crag.. the path im talking about is one of the lesser defined "paths" that lead from the "proper path" that leads from left to right infront of the crag..
so as you walk to the crag from castel helen, you eventually have to go up the blocky/bouldery area to reach to base of the crag and the routes..
the "cave" is a couple of metres adjacent to one of the approach "paths" that lead up through the boulders and scree type area.. as mentioned, somewhere infront of the quartz wall..
kudos if you can find it, its not massivley obvious.. less of a cave, more of a hollowed recess below a block.. but sorta cosy/claustrophobic?