They were waiting for daylight. If that is what they said.
That does not mean they would go in at that exact minute daylight broke. They will go in when they are also confident and ready. It's called being professional.
Jeremy had told them Sheila was a nutter, looney, psychotic depressive and knew how to handle guns. Neville had rang him saying Sheila had 'gone crazy and had got the gun'. Perhaps a good idea to not rush things.