PAN UK’s list says my council does not use pesticides so why have I seen operatives out spraying chemicals?

While the council might not be using pesticides it is possible that other land managers in your area are still using them. This might be the case with private land such as shopping centres and housing estates. Similarly, areas of a town or city (particularly roads and streets), might not be under the control of the local council and instead be the responsibility of a higher authority, usually a district or county council. 

Alternatively, a council might be using an alternative such as pelargonic or acetic acid which look very similar to pesticides when being applied.