Having worked in the British civil service myself, I can tell you that most grades dealing with members of the public are officers of some level, for example administrative officers, executive officers, higher executive officers etc. Sometimes they have a specific job title relating to the service they provide, but unless you knew what that was "officer" is a pretty generic term that covers most roles and would be understood.

So you might say:

I went to a local government office and spoke with an officer.

Having worked in the British civil service myself, I can tell you that most grades dealing with members of the public are officers of some level, for example, the historical administrative grades were administrative officers, executive officers, higher executive officers etc. At local government level, many workers are still called "government officers" (see example). Sometimes they have a specific job title relating to the service they provide, but unless you knew what that was "officer" is a pretty generic term that covers most roles and would be understood.

So you might say:

I went to a local government office and spoke with an officer.