GCP changed voices in TTS but some of the replacements seem not available

[sargearmstrong]

Dears, something odd with Google TTS. Per this PDF, they "replaced" some of the voices https://services.google.com/fh/files/emails/b_362612430_reminder_1.pdf

However, various variants all sound a like. I can't find anything to suggest why this might be, except this suggests some related chaos: https://www.googlecloudcommunity.com/gc/AI-ML/Cloud-Text-to-Speech-Voices-updating-December-in-Europ...

I specifically just want one of these voices:
https://cloud.google.com/static/text-to-speech/docs/audio/en-GB-Wavenet-N.wav (a new voice but not on sample page yet)
https://cloud.google.com/static/text-to-speech/docs/audio/en-GB-Neural2-N.wav (a new voice but not on sample page yet)

https://cloud.google.com/static/text-to-speech/docs/audio/en-GB-Neural2-A.wav (not accessible in API)
https://cloud.google.com/static/text-to-speech/docs/audio/en-GB-Wavenet-A.wav (not accessible in API)

Thank you for any guidance!