@DPRees125 Haven't yet seen them myself, so might have to see whether I can visit there this weekend. And if you're other sighting looks like it could well be griseus, then may have to definitely visit!
Its an interesting spot, there may still be Archaeosynthemis orientalis about, its still the only spot where this species has been seen in the region in recent years, including this one. for the pygmyfly you need to look in the seepage and in the bog on the northside of the pond