Cheers, I imagine you're correct that something is internally failing. CPU and Disk usage skyrocket with some of the apps or programs I used to try and fix things, so I guess they're exacerbating things a little too.

Underclocking and the linked fixes seem to have had no effect (and it seems my GPU wasn't overclocked or has any overheating issues). Doing a Clean Boot had no effect either.

I'll have a go at a full Factory Reset soon and wipe all files. I assume if that fails it indicates that it's my laptop itself that is breaking down and the only option is a new one?