Over the years, we have dug in a number of places, always (trying) to follow draughts. Currently, we have one dig where there is a very faint cold draught, which is encouraging, but as we dig, we keep loosing the draught. Then, as we get a little despondent, we move a seemingly insignificant rock, and, lo, theres the draught again.
The other dig, which has now been ongoing for nearly 5 years, originally we were digging in the lowest part of the cave following a tiny trickle of water, then again, cool draughts kept popping out from various places, some of which we followed - rather fruitlessly - until we hit the mother lode.
We are now about a further 20+m further down, having found cave in the middle, following another trickle of water. Once again, we get occaisional blasts of cold (not cool) air.
We surmise that there could be a sump somewhere that empties itself like a u-bend and sends a cold draught towards us. We know where the water ends up, and we know that there is another cave on the upstream end, so......