Hang in there, Duncan.
I went through the 'process' a few years ago and fully understand what you're talking about. I'd lived here 25 years before deciding to go through with it. Already a taxpayer....attended high school and uni here... etc etc
The hoops you have to jump through are quite extraordinary...and it feels like different people in the same department aren't talking to each other
But I got there in the end and the day on which my citizenship was confirmed was bloody exciting! Well worth the effort and time invested.
I look at that citizenship certificate today, framed and hanging on my wall, knowing what it means to have been granted citizenship, and it's something I hold in massive regard and pride.
Just stick with the process. One step at a time. You'll get there eventually.
Good luck, mate.