Hi Martyn,
Thanks for sharing the files.
The minidump files indicate hardware issue. Before asking you to take the computer to a maintenance shop, I would like to double-check it by enabling Driver Verifier.
Please enable the driver verifier and let the computer crash 3 times then disable it and share the newly created minidump file:
https://www.tenforums.com/tutorials/5470-enable...
Please do not hesitate to ask if you need further assistance.
Stay safe.
____________________________________________________________
Standard Disclaimer: There are links to non-Microsoft websites. The pages appear to be providing accurate, safe information. Watch out for ads on the sites that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the sites before you decide to download and install it.