Jim59, as your sample NOTAM (could be Lasham, Dunstable, or any club on the calendar (see BGA competition calendar on their website) mentions, gliders are usually working height bands BELOW THE INVERSION, or BETWEEN THE TOP OF ANY CUMULUS CLOUDS AND 500 feet above the ground.
They don't go anywhere if its raining, or if there is no convection. And night flying is most unusual! So if I were flying power on a good soaring day, I would fly above convection - smoother air anyhow. Or before 10 am or after 5 pm. Then you should be quite clear of glider traffic.