I could see an argument for relaxing that for mobile voicemail, on the basis that mobile phones are pretty personal and not generally shared by multiple people, but I've no idea whether that may have happened. Or, indeed, whether such policies may vary between organisations within the NHS.
Are you struggling to come up with a voicemail greeting that you believe in? Do you find that everything you record comes out too casual, overly professional, or doesn’t seem to touch all of the bases that you want it to?

The best text-to-speech voices don't sound robotic at all. Do a "text to speech" search in Google to explore your options. Type in your script and presto! You'll get an instant greeting with a natural sounding voice. You can select from a broad spectrum of male & female voices with any local or foreign accent you choose. LinkedPhone offers text-to-speech built right into our software. It's super popular and our users love it!
Creating a professional voicemail greeting isn’t complicated, but you need to keep a few things in mind to ensure success. The following tips will help: Be friendly and welcoming - let your company's personality shine!; Have a clear voice, speak at a slow to moderate pace, minimize background noise; Ensure the greeting is human and approachable; Keep the greeting short and informative; Ensure the greeting doesn’t sound robotic or unnatural; Show your gratitude for the call by saying thank you; Manage expectations by clearly stating when the client can expect a callback.