Thanks. There is definitely an issue with the IRST software churning the processor when the GUI is installed. There is a fair bit on other forums about that and I've seen it myself, although only recently, as mentioned. All my drivers are 100% up to date, although my BIOS is perhaps not.
Having said that, I'm still having the crash issue. It may be caused by a newer version of one of my other drivers, but I'll uninstall the IRST driver completely and fall back on the MS drivers in the short term as the next thing to test.