We get a lot of wasp nests in the roof void. Big pendant papery structures suspended off the rafters and the slates. They go to sleep or become very inactive at night, si if one is particularly problematic I just go up there late, and spray the nest for about a 30 second blast, then clear off. It may take a few shots over a few nights, but you’ll get them that way.
Although some sprays have different effects,…like.. one spray makes them nervous, and one spray makes them small.
Seiously enough though, attack at night, late-ish. You’ve got a bit of time before they wake up, and if you can make a clean exit and seal the loft then just spray the hive, batter the thing open and retreat very quickly, perhaps spraying through the attic hatch before closing.
A few nights ago I shovelled a live nest out of a compost heap, so that I could get the compost the next morning. I didn’t hang around for long, but by the morning they’d cleared off elsewhere, except for a few lurkers.