Country tag for United Kingdom is:
ENG
If you want play for United Kingdom HOI4 you could use tag command:
tag ENG
To annex United Kingdom in HOI4 you could use annex command:
annex ENG
To delete all United Kingdom units you could use deleteallunits command:
deleteallunits ENG
To add interests on United Kingdom you could use add_interest command:
add_interest ENG
To remove interests on United Kingdom you could use remove_interest command:
remove_interest ENG
To start occupation on United Kingdom you could use occupationpaint command:
occupationpaint ENG