Not difficult if you see the white forehead patch and the very small white tick on the wing.
Female black-and-white flycatchers can be more than a bit confusing. Unless you have them in the hand that is. This lovely female Collared Flycatcher is quite distinctive. Large club shaped white wing patch extending to the edge of the wing.
Grey rump contrasting with black tail.
Easy to see when the birds are in the hand but field id when they are flitting about in trees is a different matter . . . .