govbuntu-setup.txt

insert usb
boot machine hitting F12
select boot from usb

if you get not enough space msg boot again with F12 and go down to BIOS
set secure boot enabled to false
set System Configuration -> SATA Operation to AHCI

reboot hitting F12 then boot from USB

Ubuntu set up is straightforward but you will need to be networked so pick a WIFI connection, enter pwd and connect
You also must encrypt the laptop (but you don't need to encrypt the home dir)
once finished you might get a nouveau error, just reboot

now open a term and 

$ wget 192.168.224.157/govbuntu.key
$ sudo apt-key add govbuntu.key

add this to /etc/apt/sources.list using editor (gedit/Vi)
deb http://192.168.224.157/ zesty main

$ sudo apt update 
$ sudo apt install hmrc-setup -- you currently need to do this twice as sbt doesn't install properly first time
$ hmrc-setup