I am trying to ensure that the iOS app that I am working on is accessible and am trying to implement VoiceOver to ensure this.
One strange thing that I cannot find any h
You should definitely not change the accessibility label just to make VoiceOver pronounce things correctly (i.e. do not try "hack" the label pronounciation). The reason is that VoiceOver does not have speech output only; it has also braille output where blind users expect to read things exactly letter-by-letter as they are written (i.e. see exactly all the spaces, capital/small letters, etc.) If you did e.g. write "I D" instead of "ID", then while VoiceOver would pronounce it perhaps correctly (in the specific version of iOS), blind users, after also reading "I D" on a braille display might think that that is how it is actually written and appear let's say non-professionally when they would then use this wrong spelling in written exchanges with other people.
The correct way to deal with this, albeit without giving you an immediate solution, is:
Sorry for the bad news.
Finally, here, both on iOS 8.4.1 and iOS 9.0.2, VoiceOver with default US English iOS voice, at least on this webpage, pronounces "ID" in "Touch ID" as [ajdi:], not [id].