TheLoneRoger

I'm fairly new to Affinity Photo, so maybe there's something I'm not getting about the RAW workflow, but what actually happens when you click that 'Develop' button?
 
 Because I'm finding that often the actual image you get after you 'develop' is not the same as what you've just been working on, which makes no kind of sense to me.
 
For example, I was editing a bunch of pictures that were shot in low light, hence a little noisy, and although I managed to clean them up considerably when working on them as RAW images, as soon as I click Develop, they're full of noise again!
 
Actually, it looks more like some artful attempt at introducing grain, but that is not the effect I'm after.
 
I can post examples if you like, but maybe it's just something I  haven't understood about the workflow, in which case, please enlighten me!
Cheers
Roger