Ok - as is my own personal tradition I’m answering my own question.
To resolve my issue, when using Sound Attenuation - ensure that you are attaching it to a component on your character (Camera or Mesh). Otherwise it does jack all.
This also affects the loudness of recording being played back (voice.MicInputGain = 1) as well (because your mic recording is not being attenuated into the scene).
Sing out if you need any help in this space yourself… I’ve wrestled with 1000 variants.