Hi there. I didn't try disabling USB boot option, but boot priorities didn't work.
Windows Boot Manager didn't appear in the options. There was only my M.2 SSD, and my HDD.
I sent the machine back and the supplier has stated that the M.2 drive was replaced or repaired (they've claimed both).
Now I have the machine back and booting takes much longer.
The Gigabyte "Insist on Ultra Durable" splashscreen appears, then flickers, then a new screen - what I'd call a dos screen appears that states "Initialising Intel (R) Boot Agent GE v1.5.62 (and some other stuff), then the Gigabyte splash screen flashes up again twice (seemingly in 2 different resolutions), then another dos screen that states "Initializing Intel (R) Boot Agent CL v0.1.10, then the Gigabyte splashscreen flashes up twice again (in different resolutions again) and then the machine loads into Windows.
The whole boot takes 33 seconds which seems a bit long for a M.2 SSD.
When I checked the BIOS settings they seem much more complicated than when I sent the machine back.
In Boot priorities, previously I had 1 entry - my SSD drive.
Now I have 7:-
1 - Windows Boot Manager (my SDD details)
2 - UEFI:IP4 Intel I211 Gigabit Network Connection
3 - UEFI:IP4 Intel Ethernet Connection (2) I219-V
4 - UEFI: Intel I211 Gigabit Network Connection
5 - UEFI: Intel Ethernet Connection (2) I219-V
6 - My SDD details
7 - IBE GE slot 0500 v1562
Those all also appear under boot device selection, as well as an other:-
IBA CL Slot 00FE v0110
(Previously only my SDD and HDD appeared there)
Is all this new "clutter" necessary, is Boot Agent necessary, and is there anything I can do to reduce the boot time?
Thanks a lot for your help so far, and anything else you can suggest.