By international postal standards Northern Ireland, Scotland and Wales are not a country but all part of the United Kingdom.
The last line of your address should say United Kingdom
Not UK because that's Ukraine
Not Wales/Scotland/Ireland because if you are shipping from England it might be delivered either way, but in other parts of the world it will depend on the postman who accepts the mail or does the sorting, to correct it to United Kingdom, or throw it in the bin that says Incorrectly Addressed.
TL;DR: If you live in Great Britain, the country in your address should say United Kingdom (and not Ireland, Scotland, Wales, or UK), or you might not receive your mail.
Ireland isn't part of the UK btw, Northern Ireland is. I know it's confusing but there's a difference between [the Republic of] Ireland and Northern Ireland.