27 minutes ago, Sparkrite said:

Unfortunately as it turns out I did speak too soon !!

Continues to full crash/lock system and having to power down to recover.

Looked further and discovered that I only have a EVGA 600W PSU, I thought I had a 650W. 

Anyway have a 850W Corsair on the way, fingers crossed this cures it.

Will keep you posted, as they say.

This is very likely at least one of the major issues. 600W is way too low for your system.. even if it "works", there are likely transient issues and spikes when it's near 100% load, which could easily hard lock the system. See what happens with the new PSU. 

40 minutes ago, Sparkrite said:

Anyway have a 850W Corsair on the way, fingers crossed this cures it.

Not sure it will, but it will help eliminate one on many possible causes.  Normally when the PSU is the problem it results in immediate power cycle.

The BIOS/EFI settings can also be either a “gold mine” or a “land mine” … stick with defaults and check RAM timings.

Try Prime95, that will expose both RAM and CPU potential weakness.

Other things to try:

Make sure MB Bios/EFI is current and do a “reset to defaults” after BIOS update (4/11/2024 seems kinda old)

In Win11 from cmd (run as admin):

sfc /scannow … run multiple times if errors reported

DISM  

Assume you have rBAR disabled (default).

Run the DDU process for latest GPU driver install (run from OS safe mode, disconnect internet, manual download drivers first).

And finally, most important … ask yourself “am I having fun yet” 😉 … welcome to the land of PC diagnostics … it’s a wonderful world.