Crikey... Venus has aligned with Mars in the 5th Ascension, it seems, because I can now access the F10 boot menu.
I achieved this (I think) by pulling out every USB, LAN was already pulled out, connection except mouse and KB in the back panel when making the changes in BIOS.
Now... and cop this, now (after putting everything back in... which is only a HOTAS and rudder pedal) the BIOS seems to be like the optimised boots are enabled. Trust me, I do have these options enabled in BIOS.
Sometimes the skull will come up, then pci card text (LAN acknowledgement), then the Skull again and makes F2/ F7/ F10 selection from there. Sometimes the Skull comes up once and then straight to 'Starting Windows"... and sometimes, boot bypasses everything and goes straight to 'Starting Windows'.
BIOS won't boot at all with onboard Audio disabled and WIndows doesn't see the Audio to notify to install drivers... no yellow bang beside Audio in Device Manager.
Intel BIOS used to be excellent, faultless, trusted, consistent and for now,,, what gives??