Very unusual BSOD issue

The laptop I'm trying to fix had an attempted BIOS update. Something went wrong and now the system seems to be skipping BIOS completely. Then, it goes straight to a BSOD with an 'irql_not_less_or_equal' error. I have tried refreshing/resting the computer in advanced options, system recovery, boot repair, everything that I've been able to find or think of. After the system reset and refresh, it worked completely fine until I restarted the computer and then loop started again. I have no access to an OS on the system (installed or live disk/usb) and I can't do a reformat and clean install because I can't change the boot order (the HDD is the primary boot device) Anyone got any ideas? It really has me stumped...

Sorry for the delay in responding. There just aren't that many people who do BSOD analysis, so at times we get a bit overwhelmed!

If the system wasn't using UEFI or Secure Boot, then a UEFI update would reset the system to using it - thereby making the system unbootable (took us almost a day to figure this out at work)

It can't be skipping the UEFI, it may just be that there's no screen showing.
Usually you can access the UEFI setup by holding one of the F (function) keys when the system boots.
This will change depending on the make of the system. Try Esc, F2, F4, F8, and F12 for starters