Can anyone help me with the this tutorial for a custom maintenance free grub menu screen?

I was trying to follow the instructions here: https://help.ubuntu.com/community/MaintenanceFreeCustomGrub2Screen

I've got it showing my chosen image and colors etc, but for some reason my custom menu entries never show up.

I run sudo update-grub, but it's like my 06_custom file does not exist, and I have checked that it is definitely saved in /etc/grub.d

I have no idea what I missed, seems like i've checked everything.

Here is my 06_custom file:

#!/bin/sh
echo 1>&2 "Adding Ubuntu Admin 1, WebDev 1, and Webdev 2"
exec tail -n +4 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
menuentry "Admin 1" {
        search --no-floppy --fs-uuid --set=root c0066b5a-6197-46c7-a9a2-9093cbd6874b
        linux /vmlinuz root=UUID=c0066b5a-6197-46c7-a9a2-9093cbd6874b ro quiet resume=/dev/disk/by-uuid/993fc05d-45df-450e-b8a0-f1a31262a077 splash
        initrd /initrd.img
}
menuentry "Admin 1 (recovery mode)" {
        search --no-floppy --fs-uuid --set=root c0066b5a-6197-46c7-a9a2-9093cbd6874b
        linux /vmlinuz root=UUID=c0066b5a-6197-46c7-a9a2-9093cbd6874b ro recovery nomodeset
        initrd /initrd.img
}
menuentry "WebDev 1" {
        search --no-floppy --fs-uuid --set=root dd7ce130-14b6-48ea-bb5e-d2b37f658151
        linux /vmlinuz root=UUID=dd7ce130-14b6-48ea-bb5e-d2b37f658151 ro quiet resume=/dev/disk/by-uuid/e3c3f305-57f4-4ebc-8e8e-d04aaec71ac6 splash
        initrd /initrd.img
}
menuentry "WebDev 1 (recovery mode)" {
        search --no-floppy --fs-uuid --set=root dd7ce130-14b6-48ea-bb5e-d2b37f658151
        linux /vmlinuz root=UUID=dd7ce130-14b6-48ea-bb5e-d2b37f658151 ro recovery nomodeset
        initrd /initrd.img
}
menuentry "WebDev 2" {
        search --no-floppy --fs-uuid --set=root de946643-484e-45f3-a57a-471a6dd0ad4c
        linux /vmlinuz root=UUID=de946643-484e-45f3-a57a-471a6dd0ad4c ro quiet resume=/dev/disk/by-uuid/4ef3ac62-969e-463c-b4c8-c488b34a376a splash
        initrd /initrd.img
}
menuentry "WebDev 2 (recovery mode)" {
        search --no-floppy --fs-uuid --set=root de946643-484e-45f3-a57a-471a6dd0ad4c
        linux /vmlinuz root=UUID=de946643-484e-45f3-a57a-471a6dd0ad4c ro recovery nomodeset
        initrd /initrd.img
}
menuentry "System restart" {
        echo "System rebooting..."
        reboot
}
menuentry "System shutdown" {
        echo "System shutting down..."
        halt
}

I was ultimately unsuccessful following the instructions in the guide.

However, There is an application called Grub Customizer which essentially does the same thing. Just a whole lot easier. That'd be my suggestion for anyone struggling to follow the guide.