Southend is still in Essex. Being its own unitary authority doesn't mean its now its own county. Every ceremonial county is made up of many unitary authorities/boroughs. It is still part of Essex so should be top of the list
Perhaps accept Clacton as a type-in? Agree on the Southend issue. If it’s not in the list then Grays and Stanford-le-Hope shouldn’t be as they are in the unitary borough of Thurrock. However, all should be included as being within the boundaries of what everyone outside of local government knows to be Essex.
Southend is a unitary authority and not now technically part of Essex!