Further to my post above regarding not being able to download a later version of ESET Smart Security than v8.0.132.0, I have now managed to download v8.0.139.0 this afternoon. I have installed it on my Windows 10 system (upgraded from Win 8.1) and then rebooted.
All went fine and no sign of the previous problem resulting in the "DRIVER: IRQL_NOT_LESS_OR_EQUAL" error in epfwwfp.sys with version 8.0.139.0 during the boot process.