Some county constabularies and fire services do currently have the same appointed auditor. Back in 2016/7 after receiving notification that an authority had decided to opt into our scheme, we asked if there was a need for their authority to have the same appointed auditor as another opted-in local government, police or fire body or bodies, and why this is required.
We were able to accommodate virtually all requests, but sometimes there are contrary reasons (e.g. strategic/service partnerships with bodies from different areas).
We are following a similar approach in 2021/22.