Thanks Skipper tickets been submitted as per your suggestion.
In the meantime I’ve had a potential eureka moment. I decided to do one last try using a different (older and shittier) USB pen drive. Same process same as with the previous one but now I’m getting actual activity on the digital readout.
So it appears you might be right and the BIOS flashing was the problem. Thankfully though I (might be) on the right side of it!
Thanks for all the help guys