Just an update for anyone in the future:
I bit the bullet and bought a new PSU (a TX650M Corsair).
I will post here if the computer crashes again with this new PSU installed but otherwise, assume that this fixed the issue!
Thanks for the quick response!
I got the computer from a friend and have been using it myself for around 2 years with this power supply. He'd previously been using it for around 2-3 years before I got it I believe.
I'll test the PSU as you suggest tomorrow and get back to you on this thread...
Last weekend, I was in the middle of a Skype call when my computer (Win10 Pro) just suddenly powered off (after being on for around 1.5 hours). No blue screen error nor a beep code from the motherboard: the fans just stopped spinning suddenly and the screen turned off.
Something similar had...