Folk clubs these days seem fairly even numbers, though I imagine they vary. Back in the 60s? That's a long time ago, and I wasn't counting. Heritage was an odd one, since Oxford University in those days hade a lot more men than women, and at least officially it was university club. But there still seem to have been a fair number of women there, including guest performers.

Now sessions, that's a different matter. My impression is they tend to be heavily male dominated, this being an aspect of the pub culture, and the fact they are normally pub based. (An effect of the bizarre legal situation in England which penalises live music in any other setting even more heavilybthan in pubs, as those who have been keeping up with the PEL business will appreciate.)