I seem to recall in 2001 (foot and mouth) or thereabouts a group of diggers, possibly from Leck Fell/Iron Kiln, digging in the Eastern end of the cave.
Robbie Burke mentioned the northern passage once, not sure if he dug/pushed it but it was longer than the survey suggested.
Also, early 2000s myself and a few Black Rose dug briefly in one of the lower muddy passages but gained nothing. I seem to recall lots of mud, a large lump of rock in the way and a general lack of enthusiasm.
Sorry it's not much detail, if nobody else answers I'll have a poke about in some notes later/tomorrow, just in case there's any more info to be had.