Default [Q] Network Stuck at 'H' and never drops down to 3G

I did some searches on this and I can't find anything on this.

I've just noticed that my phone is stuck on 'H' signal, it can scale up to H+ as normal but as soon as the data has finished transmitting it will go back to 3G for a split second before returning to H and staying there. This has happened for a few days. I've noticed that my phone is getting unbearably hot (with a UV CPU and GPU, fully tested, stable) and my battery life is awful.

I've now gone back to a completely stock system, ODIN reflashed the GMK6 update (stock recovery, kernel, modem and ROM - ROM was always stock anyway) and the problem still persists.

I'm going to phone my network in the morning to see if they've done anything in the area or if anyone else is reporting the issue but has anyone else ever witnessed symptoms like this?

More background: I've recently tried ArchiPort 4.4 before going back to stock and I've been using the Devil2 kernel for more than 9 months. In the UK on the Three network, which is 3G only, no 2G.
HTC One m8, Rooted + Xposed, Stock ROM, ElementalX Kernel