Bat emergence surveys only count between May and September, and every consultant’s diary fills up in the first weeks (sample note).
If the building could hold a roost, the planning officer will ask for the surveys before a decision. Book the first visit in winter, when the inspection of the building can be done, and the dusk visits are already in the diary when the season opens.
A missed season does not only delay the survey: it can move the whole build programme by a year.