I am a blind IPhone user and have installed IOS 12 on my 6S+ device. I downloaded and selected the new Irish voices, for SIRI and Voiceover use and, in general, am very happy with them.
The only issue occurs when they read a monetary amount, in my case, Pounds Sterling. When I use a UK voice, it says, for a £50.99 amount, "Fifty Pounds and Ninety Nine pence." When I use the Irish voices, they say "Fifty dot 9 9 British Poundsies."
I have already reported this bug to email@example.com