Just an update on my current experience with the phone.
Grounding issue with the home button. I have now noticed it, this only happens when I'm holding it with my left hand, and use the right hand's pointing finger to tap it. Using my right thumb however is still fine.
The fingerprint unlock is very fast and accurate (compared to my dad's 5s). Nice to unlock the phone and skip the lockscreen.
Performance and temperature is very good, even if there is some throttling it hasn't negatively affected the phone. After an hour of gaming the phone was around ~50c according to CPU-Z. My old M7 peaked at 70c but that was during the hot summer. Using CPU-Z again it confirms only two of the A57 cores are used, but I don't need the full performance anyway.
Some apps are really confused with the menu button. Some apps will display it, some don't. And for the few and don't, sometimes they don't respond to the menu button gesture. Noticed this with Poweramp (can't change to list view due to this) and Nova (which doesn't really matter).
I'm having problems signing into sites with G+ login. It takes me to the Chrome sign in page (which says I'm already signed in) instead of actually signing me into that site. A work around I found was to sign out of Chrome, sign into the Google mobile site, and then try the G+ login again, which will work this time. Then sign back into Chrome.
The supplied typc C cable is pants. The plastic on the ends don't feel that strong, it feels like they can easily snap. Also, plugging them in and out in both ends feels light it's too tight. I bought a couple of extra type C cables from the rainforest beforehand as spares but they feel much more durable and easier to use.
The music volume via earphones seems to be a few steps lower than my M7 but the sound quality is significantly better, I can hear a wider range and it feels far more balanced. I tried MaxxAudio but decided to keep it off for now. As for the speaker itself, it's not really that loud so sometimes you can't hear the notification, but it does sound very clear.
Battery life is very good, I usually have the screen on around ~15% as it's bright enough to use indoors, and at around ~40% outside which is enough for me to see (granted it's been dull and dim for the past few days). Easily getting ~5h onscreen time and lasting me a full days use.
Camera is very good as well but the app doesn't feel intuitive to use, even though some controls are similar to the Google camera. I may stick with it for now but I do get temptations to install the Google camera.
Honestly the call quality surprised me, it's very clear and a good volume, my M7 had a slight muffle and wasn't loud enough for me (my ears are bad at listening to phone speakers

). And considering I'm on giffgaff that's a good thing

.
App permission control is nice but it doesn't seem to work for all apps. On certain apps, when you tap it, it crashes and goes back to the main settings screen instead of showing that app's permissions. Not really a biggy for me, I don't really have any apps which I feel have too many permissions.
Overall compared to my old M7 I am loving this phone even if it has a couple of issues, for a £289 phone, it's a good buy. Not a 2016 flagship killer (or 2015 even), but great for the price.