I didn't see any Common Darters last weekend at Priory Meadow (there
were 6 the weekend before, in near identical conditions), so I had
given up on the season until I saw your message.
As the forecast was good today, I went along to Brockholes, and saw at
least 3 (2 males and a female) in the expected places (fence posts in
front of Boliton and Red Scar woods). This was late morning.
I the early afternoon, the sun was brighter and hotter, but Common
Darters were less in evidence (I did eventually see 2). I didn't see
anything by the water though.