There are various holes around and to the east of ByP that skimble and myself have looked at recently:
http://www.aditnow.co.uk/photo/Bwlch-y-Plwm-Lead-Mine-User-Album-Image-73557/ but it wasn't somewhere I'd been before.
SH 629 414 - slot between boulder and rock face with pitch (3? m to floor) visible. This is between the above level and the big open workings and is on the right hand side (looking down) of a wide gully between rock outcrops.
SH 6319 4145 - level marked on 1:10,000 map. Very short trial (not out of daylight).
SH 632 413 - shaft/open working. Perhaps 7 m deep. Abseiled from tree to earth/boulder pile in open stope. Steep descent to water either side of pile. West: a shaft visible below water level but stope does not appear to continue far in this direction. East: stope continues downwards and there is possibly a level heading outby (see below), but it would involve getting pretty wet to investigate.
Level and tip east of SH 632 413 presumed associated with above mentioned open working. Water deep i.e. limited air space. Would need a major digging or siphoning effort to clear it.
SH 6347 4147 - short level to pitch down where the level is stoped out up (in one place to day) and down, Pitch is about 5 m to apparently deep water. Passage can be seen continuing beyond stope but it could only be reached by installing a bolted traverse and I'm not certain that it continues much beyond the stope. There is an old iron pump rod with an eye at one end and a forked eye at the other at the lip of the pitch. Presumably there is a lower level otherwise the water would be up to the level we came in on.
SH 6348 4149 - short trial, barely out of daylight.
SH 6371 4145 - level to north of main Hafod Boeth workings. Wet - skimble reported crotch deep-water. Level splits a short way in. Straight on went for 60 or so paces to backfilled end. Right went for 15 paces. No stoping.
Dave